The Tarrasque is basically Florida Man Godzilla. It's a pure fucking engine of destruction. Dreaded by adventurers for its high HP value and its obscenely high regeneration ability, only surpassed by Zargon the Returner in the Elder Evils book, it is known to rampage across nations eating everything. It cannot fully be killed through normal means; therefore, anyone lucky enough to reduce a Tarrasque to negative 30 HP will then have to use a wish or a miracle spell to completely destroy it, with only a 50% chance of success. If unsuccessful it will wake up again x years later and fuck more shit up. Also, no matter how big your army is (assuming your adventuring party had enough cash to recruit mercenaries), the Tarrasque's fast metabolism will allow him to produce such powerful flatulence that all your troops will die by suffocation in just one turn.
He only wakes up for 1-4 days every 2-12 months, but every now and then he stays up for several weeks before napping for several years for some reason that's never explained. Yeah, he's a heavy sleeper. Must be all the binge drinking.
Named after a famous dragon myth from the south of France, which originally featured Saint Martha (a chick from the Bible, because it totally makes sense that someone like that would be in France of all places) taming the beast with her prayers and piety, only for the people to kill it anyway once it came quietly, because man is the real monster, etc. You are welcome to try that on this version of the beast. We'll wait. With popcorn well in hand. Incidentally, this is almost certainly the origin of the shell on its back and the fierce, leonine look of its head.
As 3.Xe went on, more and more monsters were introduced to constantly one up the Tarrasque who already had to compete with Great Wyrm Dragons. In the monster manual II, we at first got the Leviathan and the Phoenix, neither of which had an comparable hit point count (though the phoenix has some fuckawesome spell like abilities, and goes boom with the force of a disintegration spell when killed, after which it promptly COMES THE FUCK BACK TO LIFE!) and Linnorms, who are massively over CRd. Nothing really similar to the Tarrasque was introduced in the other three monster manuals save for Dalmosh, who the Tarrasque would eat for breakfast, and then there was this giant prismatic...hamster...thing. But then a (lot of) challenger(s) approached when the Epic Level Handbook, and the very first monsters that were undoubtedly bigger and stronger than the Tarrasque appeared in the form of Abominations, Colossi, Prismatic and Force Dragons, Devastation Vermin, and other such shit (like the bullshit permanent HP loss inducing wights.) Then came the books of Vile Darkness and Exalted Deeds which gave us the outsider lords, then came Deities & Demigods, and the fiend folio which gave us thunder worms, after which wizards didn't make much more uber-high CR shit. The Tarrasque got a break when the Fiendish Codex 1 nerfed the fuck out of the demon lords, though the Fiendish Codex 2 kept the Lords of the Nine where they were. Then came the Elder Evils book (a fuckawesome splatbook) and now the Tarrasque was literally swimming in competitors.
But salvation came when Dragon Magazine and the WotC website offered advanced and templated Tarrasque statistics, allowing the Tarrasque to reclaim his rightful spot as the strongest creature in all of D&D. That's right, you Atropals and your other abomination pals can fuck off, the big T is number 1!!!111ONEONEONE According to some, however, the Tarrasque is actually a pretty swell guy. Well almost. The same Dragon Magazine issue that had the advanced Tarrasque statistics also introduced Time Dragons, Epic Dragons that dwarf even the Force and Prismatic dragons.
Spelljammer, as usual, had its own unique spin on the Tarrasque. Turns out, in their native environment, Tarrasques are peaceful lithovores that wouldn't harm a fly. It's just that the nitrogen-rich atmosphere of most habitable planets simultaneously super-charges their regeneration and collects in several glands in the brain, resulting in their typical murderous insanity.
Traditionally, the Tarrasque's biggest weakness was its lack of any ability to counter flying opponents. Surprisingly, both 4e and Pathfinder took steps to fix this, though they did it in different ways. 4e gave the bugger an "Earthbinder Aura" that covers a fuckhuge area -- 40 squares, bigger than any other effect in the game and wider than any other attack can reach -- in a magical effect that cripples Flight speed to 1 square a round and forces a max altitude of 20 feet... which, as the book sardonically notes, is well within the Tarrasque's reach. Pathfinder instead just gave ol' Tarry the ability to make about 6 ranged attacks a turn and the power to make fuckhuge leaps. Both games explicitly made the Tarrasque unkillable, so even Wish doesn't kill it now; when its health drops to 0 it just burrows deep underground to hibernate. Though 4e does note that Earthbinder Aura might mean that Big T is somehow tied to the earth, and as such it might (maybe) be possible to kill it if one were to find a way to "coax it off this world," whatever that means. (Shoot the Tarrasque into space. You know you want to.)
5th edition further boosts its threat level by giving it the ability to auto-pass three failed saves a day, magic resistance, the ability to reflect ranged spells back at the idiot who casted them, and the ability to make five attacks in a single turn. And that's before it gets its Legendary Actions! However, it once again lacks any long-range attacks, no longer regenerates, and while it does have decent anti-magical defenses, you no longer need a Wish spell to kill it, leading to a derogatory saying among fans of the old nigh-indestructible Tarrasque that "the new Tarrasque is basically just a big dinosaur". Granted, nothing stops you defying RAW and upscaling an older variant, but...
- 1 How to Kill A Tarrasque
- 1.1 (3.5) How to Kill A Tarrasque in 20 Easy Levels
- 1.2 (3.5) How to (unsuccessfully) Kill A Tarrasque in 18 Easy Levels
- 1.3 (3.5) How to Kill A Tarrasque in 17 Easy Levels (or 1, if you are wealthy)
- 1.4 (3.5) How to Defeat The Tarrasque in 3 Easy Levels
- 1.5 (any edition) How to defeat The Tarrasque in 1 Easy Level
- 1.6 (3.5) How to Become The Tarrasque
- 1.7 (4E) How to Defeat The Tarrasque in 6 Easy Levels
- 1.8 (PF) How to imprison the Tarrasque in an inescapable prison
- 1.9 (PF) How to Defeat The Tarrasque
- 1.10 (5E) How to Kill the Tarrasque in 1 Easy Level
- 1.11 (5E) How to Kill the Tarrasque at any level in one or two rounds.
- 2 tl;dr
- 3 See Also
- 4 Gallery
How to Kill A Tarrasque
What are its weaknesses? Well... it has a stat block. Unlike, say, The Lady of Pain the Tarrasque is designed to be tough but not totally unstoppable, un-killable or omnipotent. And if something can be killed in a game, it can be Cheesed.
The following are mental exercises, not meant for actual gameplay. In a real game, a halfway-decent Dungeon Master would come up with a creative solution, and hopefully a player wouldn't really optimize a character solely for the sake of killing a unique creature that might never appear in the campaign.
So stop bitching about how "this would never happen in a real game."
Although all this could mean jack shit if your Dungeon Master decides to strengthen the Tarrasque.
(3.5) How to Kill A Tarrasque in 20 Easy Levels
First, the feats for each level (and source book if it's not the PH):
- Human extra feat: Power Attack
- Fighter 1: Combat Reflexes, Weapon Focus: Greatsword
- Fighter 2: Improved Bull Rush
- Fighter 3: Mage Slayer
- Fighter 4: Weapon Specialization: Greatsword
- Fighter 6: Leap Attack (Complete Adventurer), Shock Trooper (Complete Warrior)
- Fighter 8: Blind-Fight
- Fighter 9: Pierce Magical Concealment (Complete Arcane)
- Fighter 10: Melee Weapon Mastery: Slashing (Player's Handbook II)
- Fighter 12: Greater Weapon Focus: Greatsword, Pierce Magical Protection (Complete Arcane)
- Fighter 14: Greater Weapon Specialization: Greatsword
- Fighter 15: Martial Study: Tiger Claw: Claw at the Moon (Tome of Battle)
- Fighter 16: Martial Study: Tiger Claw: Sudden Leap (Tome of Battle)
- Fighter 18: Martial Study: Tiger Claw: Pouncing Charge (Tome of Battle), Weapon Supremacy: Greatsword (Player's Handbook II)
- Fighter 20: Improved Initiative
- +5 Speed, Valorous (Unapproachable East), Adamantine Greatsword: 166,050 gp, provides an extra attack at your highest attack bonus when making a full attack, and deals double damage on all charge attacks.
- +1 Soulfire (Book of Exalted Deeds), Heavy Fortification, Mithril Armor: 100,000 gp + the cost of the mithril armor, provides immunity to critical hits, death effects, and negative energy effects
- Manual of Gainful Exercise +5: 137,500 gp, provides a +5 inherent bonus to Strength
- Belt of Giant Strength +6: 36,000 gp, provides a +6 enhancement bonus to Strength
- Ring of Freedom of Movement: 40,000 gp, provides immunity to grappling and movement impedances
- Ring of Mental Protection (Player's Handbook II): 110,000 gp, provides immunity to mind-affecting effects
- Mask of True Seeing (Unapproachable East): 75,000 gp, provides continuous True Sight
- 18 base from point-buy
- +5 from level ups
- +5 inherent bonus from Manual of Gainful Exercise
- +6 enhancement bonus from Belt of Giant Strength
Total Strength: 34, with a Strength modifier of +12
Attack bonus with +5 greatsword when charging:
- 20 Base
- +12 Strength bonus
- +1 Weapon Focus
- +1 Greater Weapon Focus
- +2 Melee Weapon Mastery
- +5 enhancement bonus from magic weapon
- +2 charging
Total attack bonus when charging: +43
Damage with +5 greatsword:
- 2d6 base damage
- +18 Strength bonus and a half
- +2 Weapon Specialization
- +2 Greater Weapon Specialization
- +2 Melee Weapon Mastery
- +5 enhancement bonus from magic weapon
Total damage: 2d6+29
So, you're a Human Fighter 20, standing 60 feet away from the death machine that is the Tarrasque. This is the moment of ultimate truth. If you lose initiative, you're supremely and irrevocably fucked like a bunny on fire in a bucket of gasoline with poo for a brain, since although you can survive a charge of the Tarrasque, you probably won't be able to survive the AoOs from repositioning you. If you win initiative though, with the help of some initiative-boosting items I forgot to list down then it's game time.
You spend a full-round action using your Pouncing Charge maneuver, which lets you charge and make a full attack at the end of it, while getting the +2 bonus to attack rolls on all your attacks. As part of your charge, you make a Jump check (easy enough with your ranks and Strength bonus) to activate Leap Attack, as you Power Attack for your full Base Attack Bonus, transforming the attack penalty into an AC penalty using Shock Trooper. So, you're making a full attack at +60 damage on each hit, at the cost of -20 AC and then another -2 AC from charging. Now, at this point, the damage on each of your attacks would normally be 2d6+89 (average 96) from your Leap Attacking shenanigans. However, your Valorous weapon makes you deal double damage on any and all charge attacks, shooting it up to a ludicrous 4d6+178 (average 192). This isn't including critical hits, but they're a pain to calculate in 3.5 anyway.
So then, as you charge past the Tarrasque's threatened squares, it takes an AoO against you, using its bite. It damages you some, but it won't be able to score a crit thanks to your Heavy Fortification armour, and your Ring of Freedom of movement prevents a grapple and a swallow. You then make five attacks, at +43/+43/+37/+32/+27. The Tarrasque has "only" 35 AC. The first three only miss on a natural one, giving them a 95% hit chance. For the fourth one, you activate your +5 bonus from Weapon Supremacy, shooting it up to +37, and thus giving that one a 95% hit chance as well. The fifth and final attack is where you take 10, also using Weapon Supremacy, to make it automatically hit. So then, four attacks at a 95% hit chance, and one attack automatically hitting. 0.95 * 4 + 1 = 4.8.
4.8 * average 192 damage on each hit = average 921.6 damage in total. The Tarrasque has damage reduction 15/epic, however, subtracting a total of (15*4.8) = 72 damage from (nearly) five hits, but that's still an amazing 849.6 damage inflicted on the Tarrasque's hit point total of 858 anyway. At this point, the Tarrasque should be down to -180 or -181 hit points, meaning it will be back in action in 5 rounds, and that's why I hope you've got a means to cast Wish right then and there.
(3.5) How to (unsuccessfully) Kill A Tarrasque in 18 Easy Levels
- Cleric/Master of Shrouds with the Time domain.
- Greater Rod of Maximize spell or the Maximize Spell feat and DMM or Illumian race with the Naenhoon sigil word.
- Start your turn within close range and cast Maximized Time Stop giving you 5 turns to prep.
- For five turns use the Master of Shrouds ability to summon shadows, 4 each time for a total of 20. (For this to work we only need 15 shadows assuming they all hit, but best to be on the safe side.)
- Master of Shrouds gives +2 damage to all summons, Shadows deal 1d6 str damage on touch turning it into 1d6+2 str damage.
- All shadows ready action to touch Big T inappropriately when time stop ends.
- Assuming one rolls a 1 and misses the shadows would deal a minimum of 19*3(min str damage) = 57 str damage, no save, no SR... if the tarrasque wasn't immune to ability damage.
- Even if it wasn't immune to ability damage, although Big T has a str score of 45 (only 15 would actually have to hit) and the shadow ability specifies that when a living creature has its str reduced to 0 it dies, it could be argued that the tarrasque's immunity to death effects would also apply here. Of course, it'd still take 868 nonlethal damage and stay at 0 Str for as long as the shadows keep fondling it and another day on top.
(3.5) How to Kill A Tarrasque in 17 Easy Levels (or 1, if you are wealthy)
Start off as a Cleric or Wizard. Add whatever full spellcaster PrC's you want/qualify for. Reach 17th level.
- Holy Symbol (Cleric) or Spellbook (Wizard). If you're a Wizard, you'll need to have learned the Gate spell.
- Some method of flying for around 10 rounds or so (yes, you can use a spell if you have a suitable one). Or just be able to run quickly.
Stand (or fly) far enough away from the Tarrasque so that it can't attack you. Cast Gate, to Call an Angel (Solar). You should be able to get one with at least 34 HD. Have the Solar attack the Tarrasque with Slaying arrows. Be ready to hit the Tarrasque with ongoing damage once it goes down, but stay out of melee range of it. Use the Solar's Wish (Spell Like ability) to kill it. If that fails, have the Solar cast Miracle (one of its standard spells).
Note: Anyone with 8,400 gp (including a wealthy 1st level Commoner) can also accomplish this by using a Good aligned Candle of Invocation.
(3.5) How to Defeat The Tarrasque in 3 Easy Levels
- No particular feats required.
- No particular items required.
- Be a wizard of level 3.
- Put on your robe and wizard hat.
- Cast Command Undead on an allip (it's a CR 3 monster, if you can't find any just learn to cast Summon Undead.)
- Cast Silent Image in front of the Tarrasque or Invisibility on yourself.
- Have the allip attack it. Every hit will take off 3 wisdom on average with no saving throw, and the Tarrasque has an abysmal touch AC, with no way to hit incorporeal targets.
- Once at 0 wisdom, it'll be unconscious until its ability score is restored. Cast Unseen Servant and order it to shovel dirt into the nasal passages and sinuses of the disabled Tarrasque so it can't breathe.
- Per the MM, regeneration does not restore HP lost from suffocation, so it will be stuck at negative hit points, at least until some fool unpacks the dirt from its sinuses.
- Congratulations! For defeating the Tarrasque, you're now a level 4 wizard, with 1 XP away from level 5. Make some wealth by opening a Bar and Grill on its back.
- For added hilarity, take the Precocious Apprentice feat and with some mildly lucky rolls do this at level 1.
Note: alternatively, bring many allips to the fight since Command Undead lasts for days/level. The Tarrasque's natural weapons are treated as magic, which according to the Rules Compendium gives them a 50% chance to ignore to incorporeality. In that case the Tarrasque can take down 1 or 2 allips per round.
(any edition) How to defeat The Tarrasque in 1 Easy Level
(3.5) How to Become The Tarrasque
In 3.5 D&D, start as a Psion, focused on Telepathy. Take True Mind Switch.
- Fly near Tarrasque so it can't attack you.
- Cast True Mind Switch until you run out of XP, or the Tarrasque fails its save.
- If you run out of XP, leave, earn more, then come back later.
- If it fails the save, congratulations. You now possess the body of the Tarrasque, with all its invincibility, as well as the abilities of a 17th-level telepath. The rest of the multiverse is officially fucked.
This trick doesn't work in AD&D because the AD&D Tarrasque is explicitly immune to all psionics, but AD&D psionics are shit anyways. This trick probably won't work in Pathfinder either, as the PF Tarrasque is immune to "mind-affecting effects."
(4E) How to Defeat The Tarrasque in 6 Easy Levels
- Be a 6th Level Wizard with a starting Intelligence of 20.
- Grab the Implement Focus feat.
- Buy a riding horse for 75g.
- Put on your robe and wizard hat.
- Obtain a +2 Staff of Missile Mastery.
- Cast Magic Missile on the Tarrasque while 20 squares away. With your staff and a reasonably high starting Intelligence, your Magic Missile will do more damage than the Tarrasque can resist, and hits automatically.
- Ride away from the Tarrasque until you're far enough that it can't close the distance with you in one of its turn. If you have the Wizard's Fury daily power, you can cast Magic Missile as a minor action, allowing you to use both your standard and move actions in order to maintain a distance of 20 squares.
- Repeat the last two steps a thousand more times. This will take roughly two hours.
- Congratulations! For defeating the Tarrasque, you are now level 18.
- For added hilarity, have some friends roll Warlords or other basic attack factories with their own horses, and switch off leading the Tarrasque while receiving extra basic attacks which can be used to fire more Magic Missiles.
- Beware the Tarrasque's burrow and action points - without action points it can't try to get a lucky shot on you or your horses. While burrowing, it cannot be seen but it can still be attacked, and your attacks are automatic hits - your magic missile simply veers into the tunnel it created and pops it in the ass. The rules never state that burrowing removes line of sight, only that the creature cannot be seen, which is different (for example, you can still attack an invisible enemy or an enemy you cannot see due to blindness.)
(PF) How to imprison the Tarrasque in an inescapable prison
- Create a Demiplane and make it permanent
- Make a permanent magic portal to it
- KO the Tarrasque and planeshift to that plane with it
- Cast Imprisonment on it or at least keep it underwater to stop it from waking up.
- Cast Greater Create Demiplane to make this plane have the dead magic trait, blocking all planar travel except the portal.
- Leave the plane and destroy the portal, ideally on both sides (Remote detonation of explosives, even as simple as throwing a lit torch through the portal, sending Constructs to do it or making the portal on a separate, non-permanent, demiplane are the easiest way to accomplish this.). If you really want to be sure, you never make any portal in the first place then get off by killing yourself to pop up in a Clone on the prime material or have a construct use a magic item to bring the KOed Tarrasque to dead end plane.
This still requires you defeat it the old fashioned way though. Fortunately it's no longer the most powerful monster: That would be Great Cthulhu, who, while not a god, may as well be one. Bestiary 6 had a fetish for unkillable monsters above CR 20 and now we have giant Qlippoth lady-mushrooms with a reach of over a mile Giving birth to Quippoths from blisters.
(PF) How to Defeat The Tarrasque
By tricking it into thinking you turned it into something harmless and mortal, like a squirrel. See, its regeneration is technically just another ability in its stat block. It even follows all the normal rules for special abilities, like specifically being extraordinary, so it still works in antimagic fields. So since Baleful Polymorph removes all extraordinary, supernatural, and spell-like abilities, that would include its regeneration, which would render it mortal. There's just one little catch. Baleful Polymorph only does that on the second save, and since the Tarrasque is immune to polymorph effects, it never even reaches that point.
Enter Baleful Shadow Transmutation. This spell does functionally the same thing as Baleful Polymorph, but puts the save in the opposite order. It doesn't matter if you're immune to polymorph effects, because the spell just starts off by tricking you into thinking you were polymorphed, causing you to lose all those abilities... like the Tarrasque's regeneration. Sure, you still need to overcome SR 36 and +12 Will, but that's comparatively easy.
- Androids and anyone with access to the Nanite Bloodline (which can be obtained via Sorcerer, a bloodline granting archetype, the Eldritch Heritage feats, or variant multiclassing) have an ability called Nanite Surge that lets them, once per day, add their character level +3 to any roll, including spell resistance checks. This makes bypassing SR36 automatic at level 16+, and doable even earlier with more anti-SR effort. There's other ways around it, but ultimately spell resistance isn't a problem if you build for it.
- Boost the DC as high as you can. Ways to do this include
- By level 20, it's easy enough to have a solid 34 in your casting stat (18 base +5 levels +6 headband +5 tome = 34). This makes the base DC 22+spell level (typically 6 for BST).
- Heighten Spell lets it be a level 9 spell, increasing the DC by 3
- Spell Focus and Greater Spell Focus collectively increase the DC by +2
Now you just need the Tarrasque to fail a DC 33 Will save, and with a +12 bonus, that isn't looking too likely. It would need a natural 20 to pass. Conversely, you have at least a +20 to Will (+3 headband, +12 base, +5 resistance), so that DC 27 save against its frightful presence isn't looking too difficult.
Congratulations. You now have 24 hours to kill the Tarrasque, before it realizes you didn't actually turn it mortal.
(5E) How to Kill the Tarrasque in 1 Easy Level
- Be an Aarakocra or winged tiefling cleric, sorcerer, or wizard. Cleric is the optimal choice here, as Sacred Flame is better than Acid Splash and aarakocra get a Wis boost.
- Choose as one of your cantrips either Acid Splash or Sacred Flame (as both require a Dexterity saving throw, and the tarrasque has a +0 Dex save and advantage, it'll fail about 36.1% of the time).
- Fly 85 feet above the tarrasque
- Repeatedly cast your chosen cantrip at it, flying down 25 feet to be in range and then flying 25 feet back up (both cantrips have a range of 60 feet).
- Spend 1 hour blasting away.
Win. Die, because it's trivial for the Tarrasque to cover 85ft, even vertically, and kill the caster. The thing is already 50 feet tall, it has a 20ft reach on it's tail, and +10 to all Str skills, that's more than enough to hit a target 85ft away by jumping at it. Read better. Win. 85 feet above them, not 85 feet above the groundDie again because the Tarrasque can just hold it's action so when you dive down into range it will then jump and get you for sure.
(5E) How to Kill the Tarrasque at any level in one or two rounds.
- Conscript 1,500 Wood Elf Commoners, arm them with longbows
- Conscript 1,500 Clerics of the forge.
- Have the clerics use their "Blessing of the Forge" feature to enchant the longbows so they are all +1 magic items and then give those longbows to the elves.
- Start shooting
- If the Tarrasque is still alive, then move 35 feet after loosing the arrows.
And now the math behind that statement.
In 5e a crit will always hit, and always do damage:25 Ac or not. So if 20 commoners shoot at the Tarrasque, mathematically 1 of them will hit and will do double damage due to the crit. The issue being that if you have 400 commoners shooting only about 20 of them will hit so you need a number of commoners high enough that even if 1/20 of them hit you will still do notable damage.
The Tarrasque has 676 hit points, While the average result of a D8 is 4.5. So you need 150 average damage rolls from a weapon that does D8 damage to kill the Tarrasque, but that's a base damage hit, not a crit. The average crit is double that at 9 damage, meaning you actually need 75 crits to do 676 damage to a Tarrasque. However the Tarrasque's "Frightful Presence", means any creature within 120 feet of it will likely be frightened and have disadvantage on the attacks. So our commoners now need to get a 20 twice on two different dice, a 0.002% chance.
To get 75 crits we first need 20 times that, for 1,500. Which all things considered is not an absurd number, there were far more longbow men at the Battle of Agincourt for example if we look to history and those were trained soldiers. But with disadvantage 1,500 commoners shooting at the Tarrasque means only about three will hit. To spare you the rest of the math to get 75 crits with disadvantage requires 750,000 men. In One place. All shooting at One target. That's more people then were on fucking D-day. While the total number is better then that since about 20% of the time even a commoner will pass the Frightful Presence roll that is still beyond possible.
But "Frightful Presence" has a range of only 120 feet. If a range weapon was used that had more then 120 feet of range then we only need 75 crits, bringing us back to the reasonable 1,500 number. The longbow is the only candidate in D&D and as mentioned there is historical precedent in reality for that many trained archers being at one location so a even a strict DM would find it hard to object to this plan, and commoners are suppose to obey their lord when a muster is called so basically any well off noble or half decent or even bad king could pull this kind of draft off (assuming the nation is so poor it can't muster 1,500 trained soldiers), again lot of historical examples of this happening in countless political systems. In 5e when you make an NPC a race it gains that races traits, including in this case the wood elf weapon proficiency with longbows. So a wood elf commoner would know how to use the longbow. The cost to arm 1,500 elves is the sticking point with this plan: it would take 75,000 gold. But one could also make a strong argument for them already having them for hunting and home defense at least depending on the culture.
So with the army raised you approach the tarrasque to 130 feet, (we get closer then the longbow's max 150 range to allow the whole army to start shooting but it still means our ranks need to be less then 20 feet deep if we want the back ranks to be able to fire). If we get all 1,500 arrows in the air then we could get all 75 crits we need in the first volley, dropping the tarrasque in one round, but that required number of crits is of course on average and there are only "Lies, damned lies, and statistics" to quote a phrase. So there is a decent chance the Tarrasque is still alive. So now the whole army uses it's movement to take 35 feet (+5 due to being a wood elf) move back.
The Tarrasque now has three options: First it could with it's 40 speed step forward, but this puts it more then 120 feet away so it can not use Frightful Presence to impose disadvantage (130+35=165-40=125). or it can dash to get 80 feet closer so that next turn it can be in range no matter what the army does, but Frightful Presence is an action and dash is also an action, so either way it can not use Frightful Presence, and it's going to be point blank to an army of 1,500 longbow men, and unless the rolls are truly terrible they are going to do another 75~ish crits, to it next turn, mathematically doing twice the average damage of it's hit point maximize. It's third option is to run away like a little bitch, but supplying 1,500 men in the field is not impossible as proven countless times in history so one can easily give chase and repeat until it's over a border and it's no longer your problem.
If you were feeling fancy one could pad those numbers with a second reserve force of 1,000 troops behind the first line so that if the Tarrasque did to grip with the first line, (after taking 3,000 arrows to the face and about 150 crits), the second line could fire into the large target that is the Tarrasque as it's chews through the first line finishing the job as it would be badly bloodied from taking that many crits.
So why the clerics? Because the Tarrasque has total immunity to all non-magical physical damage, including fall damage, and total immunity to fire and poison, so you need a magic weapon or magical ammo to scratch it. So why clerics instead of magical ammo? It depends really on the setting. The 5e DMG says this about magic items: "If your campaign allows for trade in magic items," Meaning in some settings buying magical ammunition may not be possible. Conversely if your dwarves for example are as forge happy as standard dwarves then across the whole of a dwarf kingdom you could easily scout up a thousand and a half of them, (but at that point your reaching across a border so example your GM to make just that step a quest and a half to even get there support). Conversely if that's not the case you'll have to look else where to get the magical support to cut through the Tarrasque hide.
One final note is remember that the DM can bend the rules. Yes, strictly speaking the Tarrasque can only be able to turn five peasants a turn into a red mist if it get's that close, but if you think your DM is actually going to roleplay this encounter that way you have another thing coming (and that thing being a cup of commoner smoothy).
Of course this all goes a far beyond D&D as an RPG and starts becoming a war game but it's not impossible at all for players to pull off, nor had D&D not dabbled in doing just that. With Roleplay any player with a noble title, something a seasoned adventurer could acquire, and can be acquired at level 1 with the noble background call up, or at least have the connections to speak to somebody who could call up, the requisite levy of troops. This is also the option on this page least likely to have your DM strangle you for attempting. Indeed, attempting to execute on this option will turn your entire game for a dozen or more sessions into form the next Great Alliance of Man, Elves, and Dwaves, which is a campaign hook onto it self. The only draw back is time. When the Tarrasque start's rampaging it's too late, but if you have window of time where you know it's coming, you can prepare a welcoming for it.
However be forewarned if you think to try this against any other version of the Tarrasque: you will be found wanting. The 5e incarnation is the weakest of the Tarrasque's lacking damage reduction and it's signature hyper regeneration. Compared to the 3.5 version, a damage reduction of 15 does not just mean 'you do 15 less damage' it means 'you need to do 16 damage to hurt it at all,' and in our commoner army scenario the most they can do is 16 damage (reduced to 1), and only on a max damage crit, and 3.5 had less generous crit rules to begin with. Without Damage reduction the Tarrasque, or any big beast, can be killed by a thousand bug bites. But with Damage Reduction it means that only Heroes (or siege engines) can hurt, and kill, the Tarrasque.
WHAT'S THAT YOU SAY? YOU CAN FLY? YOU THINK YOU'RE SAFE NOW? THE TARRASQUE HAS ONE THING TO SAY!