Expect huge amounts of derp and rage, punctuated by /tg/ extracting humor from it.
Pyrovores are a Tyranid unit widely considered to be the worst unit in all of Warhammer 40,000. Introduced in 5th Edition, they were representative of Robin Cruddace's awful, awful Tyranids codex, in which at least half of the units had absolutely no idea what they're supposed to be doing or were so abysmally awful at what they were supposed to be doing that no one ever took them.
But by some miraculous act of the Emperor, GW isn't shit anymore and has recognized the uselessness of the Pyrovore. The 8th edition changes finally made the Pyrovore into a surprisingly decent enough murder machine.
Pyrovores are living fuel refineries for the Hive Fleet. They gain said fuel by eating. They can pretty much eat anything, from organics to inorganic material like rocks or metal, which they're able to digest thanks to the corrosive acids inside their stomachs, which explode if they get bumped too hard. Or, if you enjoy the taste of brain bleach, they're giant walking prematurely-ejaculating penises with fire instead of spunk.
A Pyrovore has two brains: one for that lumbering hunk of fail that eats like an obese kid, and another for the giant flamespurt cannon on its back. This allows the Pyrovore to devour everything like a neckbeard eating meatbread while the cannon keeps watch. The funny thing about this is that its cannon is much smarter than the beast itself; the Pyrovore is only driven by its need to eat while the cannon's smart enough to target enemies on its own. This might very well explain why the Pyrovore's terrible in melee combat.
Why the Hive Fleet thought it was a good idea to put a derp-grade brain into a beast that needs a modicum of intelligence to handle itself in combat, especially given its ability to explode, while putting the smart brain on a gun, which really isn't that powerful compared to the other races, and make them incapable of working together, begs the question: why?. Sure, it can be vaguely likened to how a tank is naught but a giant moving hunk of medal without the operator's driving acumen, but even that proves flimsier than one would like.
How Bad Is it?
5th Pyrovores are worse than Old One Eye, a DISTRACTION CARNIFEX special character in a codex that hates DISTRACTION CARNIFEXES, who is renowned for costing MORE than a Land Raider and dying to a stiff breeze... but at least he has a general idea of what the fuck he's supposed to be doing and would be tolerable if he was cheaper.
Pyrovores are worse than Chaos Sp... uh, that one Chaos unit that was terrible in 5th ed... but they got a proper Phil Kelly-granted buff in the newest Chaos Space Marine codex, and before that they could occasionally win assaults in large area terrain.
Pyrovores are worse than Mandrakes, the worst infiltrators in the game... yet at least Mandrakes have better fluff (thanks again, Kelly) and don't need a pain token to shoot anymore. They also traded a 5+ invul for Stealth and Shrouded in 7th; 8th made them truly great.
Pyrovores are worse than Flayed Ones, who are weak "assault specialists"... though they had cool, grimdark fluff and passable crunch prior to the 5th edition Necron codex, they don't harm their side when they die and there's a chance that they can come back via Reanimation Protocols and be used to contest objectives or support assaults. The 7th edition codex added Shred, AP5 in CC, and fear combined with a significant decrease in points; 8th gave them a shit-ton of attacks so they've been viable for a bit, though 8th edition is also the first time Necrons as a whole aren't overpowered, which may make Flayers look better or worse than they actually are, depending on who you ask.
Pyrovores are worse than Fire Warriors in melee, who are unceremoniously chopped up in seconds... but at least that's funny, things have gone wrong when squads assault Firewarriors, they can do that "Overwatch + Markerlights + other squads nearby can Overwatch for them + Markerlights", and can kill Land Raiders in melee with EMP Grenades.
Pyrovores are so bad that fluff writers try to forget that they even exist. In fact they appear only in one BL book (The Last Ditch) and they are as terrible there as on tabletop. Cain actually obliterates majority of incoming tyranid horde by shooting a few pyrovores, the resulting explosion wiping out most of the tyranid attack, including the Hive Tyrant and his guards. They're even being mocked by in-universe characters as terrible; which we choose to take as further proof of Sandy Mitchell's awesomeness by taking the now memetic godawfulness of the Pyrovore and making it canon.
Pyrovores are so terrible that why they are even a thing remains a point of debate because holy shit, who in their right mind would think that this... this... thing... was a good idea? It serves no conceivable purpose, and there are much better platforms for a flamethrower in the Tyranid bestiary than the body of an indirect fire mortar carrier never intended to even get in visible fucking range of the god damn enemy. I mean fuck, there's even one in the same motherfucking Codex, all you'd need to do for the Tyrannofex is light its acid spray on fire and then BAM! You have a flamer on a non-shitty platform. Or Warriors or something, because they're basically crapsack Terminators and Terminators get a Heavy Flamer! Or just anything!
They look almost identical to Biovores (a unit that is a cheap source of assault pie plates that can also be used as a barrage, and has one of the derpiest faces around), but they have a much newer, much less derpy model (although their gun does look strangely like an erect throbbing penis). As such, pretty much everybody buys the Pyrovore models and uses them as Biovore. But this has the possible side effect of convincing GW that the Pyrovore is actually good...
Also they make for great new years eve fireworks.
Why are they so bad?
Alright, spleen's been vented enough, so let's get real for a moment.
The biggest problem comes down to the fact they're in the Elites slot, which is easily the most jam-packed slot in Tyranids. They're competing with: Hive Guard (who are good at taking down transports and one of the best shooting units in the 'Dex); Zoanthropes and their Neurothrope brood leaders (incredibly powerful psykers that can throw down an ABSURD amount of mental dakka each turn); Venomthropes (an excellent support unit that provides mobile cover, defensive grenades, and hilarious 2+ Poisoned attacks); Malanthropes (quite powerful in their own right but Forge World only); Lictors (who, while not being particularly good, can at least claim their ability to not have Deep Strikers who land within 6" of them scatter); Haruspexes (while not particularly good, at least competent enough); and Maleceptors (who... well alright, they're pretty shitty but not as bad as Pyrovores).
Additionally, they have one of the most schizophrenic loadouts in the game. It can ignore armor saves (and hit at S5) by dropping its attack stat to 1... but with only one attack per model, and the rest of their stats make them absolutely awful in close combat, including I2 and WS3. They're too slow to keep up with an assault-based army, and largely pointless there anyway since once the rest of your army gets in close, since there's nothing left to flame; in a shooting army they compete with Hive Guard (which are basically the only way 'Nids can take down light vehicles efficiently). Their Flamespurt ability is AP 4, meaning you can't take out MEQ with it. They can explode, which could see them used as a suicide unit... except that affects your units as well. Your pitifully weak, vulnerable-to-AoE-explosions units, Plus it's only when Instant Death is inflicted, which means melta or krak missiles... but it dies much easier to massed bolter shots. On top of that, good luck just getting the damn thing in close enough to actually have it affected. Not to mention that wasting an extremely valuable Elite slot on a expensive-for-its-cost suicide unit is just stupid.
The wording of its exploding ability is so poorly written that when the rules are applied exactly as written, whenever one suffers Instant Death, ALL UNITS ON THE BOARD suffer a number of hits equal to all non-Pyrovores within D6" of it. This means that the Pyrovore is so bad its abject shittyness transcended its rules and altered the minds of its writers to make it even worse. Exact text:
"Volatile: If a Pyrovore is slain by a Wound that inflicted Instant Death, every unit suffers a Strength 3 AP- hit for each model (excluding Pyrovores) within D6" of the slain Pyrovore (resolve damage before removing the Pyrovore as a casualty)."
What they wanted to write was that each model within D6" suffers a S3 AP- hit. Meaning that for a squad of 10 Guardsmen next to the Pyrovore, they suffer 10 hits. What they instead wrote means that every unit on the board suffers 10 hits. Theoretically hilarious if you had a way to detonate it intentionally and brought nothing but T6 - but you don't.
So, all in all, the worst fucking unit in the game. Completely pointless, no idea where it wants to be, competes with good units (units that are basically compulsory if you want Tyranids to win). The other thing is that it had never been good: it was bad in the previous Codex (where it debuted) and it was bad in 6th, too. Countless ideas are thrown about to unfuck the unit, and you can almost see how it's suppose to work: Tyranids have trouble dealing with things in cover, and this thing is made to deal with things in cover -- so perhaps if they were beasts, had higher WS, BS, and Initiative and were allowed to fire the flamespurt in close combat like a stegadon? But the cocksucking piece of shit is fundamentally contrary to the basis of the entire army. To make it fit, homebrewers have pretty much had to make the pile of fail unrecognizable from its origins. It is that bad.
Or is it?!
With the return of our beautiful Mycetic Spore (now called the Tyranocyte) in the Leviathan Supplement, Pyrovores now actually stand a chance in filling a niche in your army as an effective stealth and shrouded eradicator! A very specific niche, but a niche nonetheless!
"But wait, PyrovorefanXX1!" you ask. "Pyrovores could do this in the old codex but were still classified as 'cess, what's changed now"? Well firstly, Pyrovores did get buffed! They went down 5 points, gained an extra wound (acid blood, yay), initiative, attack and Acid Maw and Volatile did realistically get better if you do the math. However, their form of accurate deepstrike got lost, forcing them to trudge across the board and retain the reputation they had.
But now that they have that deep strike option back combined with their 6th ed improvements, paying 220 points isn't that bad for 9 wounds worth of reasonably durable heavy flamers (which people will hesitate to try and ID that close to their troops) backed up with an effective gun platform in the Tyranocyte. With the default pressure from very common standard stuff like flying Hive Tyrants, Mawlocs, more Tyranocytes filled with Devilgaunts or other Monstrous Creatures, they stand a very high chance of being left alone to wreak havoc multiple turns.
But in saying that, they really can't do much without the Tyranocyte, so those games you would rather have your Tervigon getting all intimate with some tanks because your opponent lacks infantry basically leaves your Pyrovores on fat, lazy, old guard dog duty for some objective in the middle of the board.
HOLD THE PRESS!
... cause 8th edition came out (for good or ill) and everything changed, including Pyrovores! That's right, proud winner of "41st millennium's worst unit" for years is now much more viable, with the stats of an heavy flamer mounted on a melee fighter that hurts ENEMY units when taking damage in close combat and packs rather nasty CC attacks as well, and has a range that's coincidentally just long enough for it to attack as soon as it gets out of a Tyrannocyte. Here is the statline from the book of Xenos 2 from 8th edition:
As of Chapter Approved 2018, the cost has been reduced to less than 30 points per model. Let's recap - heavy flamer on a mini-monster, a CC weapon with AP-3 that is quite effective against MEQs, LOTS of wounds, taking wounds causes its victim to get hit and can hit a squad with nastiness if it dies. It's over lads, [[JUST AS PLANNED|the meme is finally dead! Pyrovores aren't utter shit anymore.
|Leader Organisms:||Broodlord - Hive Tyrant - Swarmlord - Tyranid Warrior|
|Small Creatures:||Gargoyle - Genestealer - Hormagaunt - Ripper - Termagaunt|
| Biovore - Hive Guard - Lictor - Neurothrope - Pyrovore |
Ravener - Tyrant Guard - Venomthrope - Zoanthrope
|Monstrous Creatures:|| Carnifex - Dimachaeron - Exocrine - Haruspex - Malanthrope |
Maleceptor - Mawloc - Tervigon - Toxicrene - Trygon - Tyrannofex
|Gargantuan Creatures:||Cerebore - Dactylis - Hierodule - Malefactor - Nautiloid - Viragon|
|Flying Creatures:||Harpy - Harridan - Hive Crone|
|Bio-Titans:||Dominatrix - Hierophant - Hydraphant - Viciator|
|Other Organisms:|| Bio-Weapons - Cortex Leech - Mieotic Spore - Mucolid Spore |
Mycetic Spore - Spore Mine - Sporocyst - Tyrannocyte - Zoats