Cortex Leech

From 1d4chan
Face full of alien wing-wong. Tyranid Edition.

Cortex Leeches are loathsome creatures resembling Rippers that leap onto the face of their victims and insert long feelers into their ears, nose and eyes. If that sounds suspiciously similar to the Facehuggers from the Alien films, then it most likely is; albeit its role is different from Ridley Scott's crawling dick-vag. The Cortex Leech's feelers are capable of manipulating and connecting to the new host's brain and their central nervous system, forcing them to become a dribbling puppet under the sway of the Hive Mind.

Essentially, they're the Tyranid equivalent of the mind control spores from the DC comics supervillain Starro. And they look like cockroaches with teeth and tentacles.

Allegedly, under the right conditions can infect things up to and including titans.

The best way to deal with them is to wear a gas mask, equip yourself with a Flamer and raise holy bloody merry on these overgrown house lice.

Tabletop Fan-Rules[edit]

7th edition[edit]

Cortex Leech Swarm 35 pts | WS 1 | BS 0 | S 2 | T 2 | W 3 | I 2 | A 3 | Ld 5 | Sv -

Brood: A swarm of Cortex Leeches consist of 1-5 bases and they take up an Elite slot on the Force Organization Chart. Only one brood of leeches may be fielded and regardless of how many bases are purchased, they form and operate as one brood.

Bio-weapons and biomorphs: Cortex Leeches have scapel-sharp teeth and excrete a powerful anesthetic that allows them to go unnoticed until it is too late. They possess the equivalent of flesh hooks.

SPECIAL RULES Ambush: Must deploy as a Lictor, with the following exceptions:

  • May Deep Strike into water terrain features in addition to area terrain.
  • If the Deep Strike roll would cause the Cortex Leeches to arrive on or in base contact with an enemy unit, treat them as moving to assault the enemy and place them accordingly rather than circling around the first base.
  • They are not destroyed if they Deep Strike within 1" of an enemy and they may assault the turn they arrive.

Diminuative Swarm: Cortex Leeches are tiny organisms, dwarfed even by lowly Rippers. As such, they mass together to have any chance of successfully taking prey. These little creatures are hard to see until they are close enough to strike. Cortex Leeches follow all the rules for Swarms as found on page 75 of the 40k rulebook, with the following differences:

  • The Cover save improvement granted by the Small Targets special rule is improved to a total of +2.
  • Cortex Leeches always have at least a 5+ cover save, even when out in the open.
  • In order to successfully shoot at a unit of Cortex Leeches, a unit must check to see if it is within a number of inches equal to the highest Initiative value of any model in the unit. If the unit does not notice the leeches, then they may fire upon another viable target. A unit never has to test for Target Priority to ignore a brood of Cortex Leeches.

A unit that contains a model with an auspex can detect Cortex Leeches at 4d6 inches rather than using their highest Initiative value.

Sneak Attack: Cortex Leeches must use cover to effectively strike at an opponent. If they assualt an enemy that was not aware of the unit (see Diminutive Swarm) or an enemy the turn they arrive via Ambush, then the Cortex Leeches will hit on a 3+ that first Combat Phase. On subsequent turns, the leeches must use their Weapon Skill, which varies depending on the terrain they are in.

If the Cortex Leeches are in open terrain, they are WS 1. If they are in area terrain of any type, they are WS 2. If the Cortex Leeches are in water terrain features, then they are WS 4.

Go for the Brain Stem!: A Cortex Leech burrow through its victim until it reaches the seat of the host's brain. It then clamps onto the stem and severs the brain from the rest of the central nervous system. The Cortex Leech then bonds with the nervous system and takes control of the body, acting as the brain. When this happens, the victim is irrevocably dead for all intents and purposes.

Cortex Leeches may re-roll failed To Wound rolls as if they had weapons with the Living Ammunition special rule (they are the Living Ammunition in this case).

Wounds caused by Cortex Leeches cause Instant Death to targets as if their Strength was 10. Targets wounded but not killed by a Cortex Leech (i.e. T 6 models and above) take no wounds from a Cortex Leech. Because wounds caused by Cortex Leeches inflict Instant Death upon their targets, bionics, ork bioniks, Feel No Pain, and any other similar wargear or special rules cannot save a victim. Regular Armour saves or Invulnerable saves are all that stand between a victim and brain-death.

Models slain by Cortex Leeches become Mind Slaves under control of the Tyranid player (see the Mind Slaves rule).

Pathetic: Against foes whose WS is at least 4 greater than the leeches current WS, Cortex Leeches require 6s to hit.

Also, if a Cortex Leech brood ever loses combat and they are outside of Synapse Range, they pass a leadership test at the end of the combat or lose a number of wounds equal to what was rolled over their Leadership.

Cortex Leeches cannot capture table quarters, hold objectives or count as scoring units.

Mind Slaves: Models killed by Cortex Leeches immediately become Mind Slaves under control of the Tyranid player. The control of the Cortex Leech within the host body is not perfect and these Mind Slaves lurch along ungainly in marionette fashion.

Treat the casualties as normal for purposes of Victory Points, and replace the fallen models either with an appropriate one or mark them with a counter. They retain all wargear and gain the following Stat adjustments and special rules.

  • -2 WS, -2 BS, +1 S, +1 T, Initiative becomes 2, Ld becomes 5 (These adjustments are not modifiers but are replacements to the model's actual stats, meaning that a marine mind slave would have an actual Strength of 5 prior to doubling for a powerfist).
  • Slow and Purposeful USR
  • Fearless USR
  • Instinctive Behaviour and Immunity to Instant Death within Synapse range (as Tyranids)
  • Move Through Cover USR
  • May still use Codex specific wargear (i.e. bionics, direswords, kai-gun, etc, etc).
  • They have 1 wound, regardless of their starting number.

Mind Slaves cannot

  • Make psychic tests, use automatic powers (i.e. warlocks) or activate force weapons and similar wargear
  • ride bikes or jetbikes (they immediately dismount and move on foot)
  • ride in transports or operate vehicles
  • benefit from any special rule not listed above (i.e. exarch powers, Rites of Battle, Stubborn, the list goes on and on).

Mind Slaves keep all wargear they were equipped with at the start of the game (unless it had a limited number of uses and was already used up). They may use any wargear they have, such as bionics or powerfists, subject to the above limitations.

Mind Slaves may attack in the assualt phase after they were spawned and they count as charging although the target unit does not go at Initiative 10 for being charged through cover (such is the surprise of their allies). Mind Slaves do not count as scoring units and they cannot hold objectives or table quarters.

The following models may not be made into Mind Slaves: Any model with the Necron Special Rule, any warp-spawned unit (Enslavers) or any unit that counts as a Daemon, undead, Tomb Spyders, any vehicles, any artillery pieces, Rubric Marines and Rubric Terminators, and C'Tan. Cortex Leech swarms can still lock such units in combat and they still inflict Strength 10 Instant Death on models wounded by them (such as Necron Warriors or possessed).


Example Mind Slaves

Hive City Ganger Mind Slave Ws 1| Bs 1| S 4| T 4| W 1| I 2| A 1| Ld 5| Sv 6+ Equipment: Combat Weapon, shotgun, flak-jacket. Rules: Fearless, Slow and Purposeful, Move Through Cover, Instinctive Behaviour, Non-scoring

Astartes Sargent Mind Slave Ws 2| Bs 2| S 5(10)| T 5| W 1| I 2| A 2(3)| Ld 5| Sv 3+ Equipment: Bolt Pistol, powerfist, frags, bionics Rules: Fearless, Slow and Purposeful, Move Through Cover, Instinctive Behaviour, Non-scoring (notice that it loses ATSKNF and any chapter specific special rules).

Obliterator Mind Slave Hah hah, just kidding, this model counts as a daemon and cannot be a mind slave.

Striking Scorpions Exarch Mind Slave (had Shadowstrike prior to enslavement) Ws 3| Bs 3| S 4(8)| T 4| W 1| I 2| A 2(4)| Ld 5| Sv 3+ Equipment: Scorpion's Claw, scorpion chainsword, mandiblasters and plasma grenades (must choose to to either strike at I 1 with S 8 or strike at normal I with S 5). Rules: Fearless, Slow and Purposeful, Move Through Cover, Instinctive Behaviour, Non-scoring (notice that it loses Shadowstrike once enslaved).

Now for a non-specific example. A chaos lieutenant with Daemonic Toughness is enslaved (he does not have enough gifts to qualify as a daemon and thus is a viable target). Prior to enslavement, the model had a Toughness of 5 but still counted as being T4 for purposes of Instant Death. After being enslaved, the lieutenant has a Toughness of 6 although it still counts as being T5 for purposes of Instant Death.

Cortex Leech Swarm

Cost: 70 pts

A cortex leech swarm takes up a single Elite slot.

Insidious: Cortex Leeches infiltrate throughout the entire battlefield, lurking in puddles, crawling amongst rocks and clinging to undersides of leafy plants. However, they are cowardly and their instincts to hide and remian unseen conflict with the goals of the Hive Mind. As such, they are not deployed as a tangible unit and start the game in Reserves, regardless of the mission rules. Roll the die for them as normal, starting on the second turn. If the die indicates that they arrive from Reserves, proceed to the Ambush rule.

Ambush: When the Hive Mind exerts sufficient force, the leeches abandon their instincts and agressively leap at their victims. Place the flamer template anywhere on the board so that it at least touches any piece of area or water terrain. Do this at the end of your movement phase. Any models whose base is even partially touched or covered by the template is subject to a single hit as if targeted by a weapon with the following profile;

Range: Template, Str 2, Special: Living Ammunition, Flesh Puppet

Flesh Puppet: If a model is wounded by this attack, they may suffer Instant Death as though wounded by a Strength 10 weapon. If a model is killed by the Cortex Leeches, it becomes a Mind Slave under control of the Tyranid player. See the Mind Slaves special rule (2nd post of this thread).

Models immune to Instant Death or possessing a Toughness of 6 or greater can never be wounded by Cortex Leeches or turned into Mind Slaves.

Conversely, models cannot benefit from bionics, ork bionics, Feel No Pain or other special saves conferred by wargear or special rules, beyond regular Armour or Invulnerable saves, to avoid suffering a wound or being slain as a result of a Cortex Leech attack.

Regroup: The Hive Mind demands total obedience from its fleshy embodiments, though the leeches are surprisingly independant until they implant themselves into a host. If the Cortex Leeches have arrived from Reserves, even if they could not make an attack, roll a D6 at the start of all of your following turns. On a result of a 2+ the leeches obey and strike again at the end of your movement phase. They can potentially return again and again, regardless of mission length or when they frist arrived. However, should the D6 ever result in a 1, the leeches' instincts prevail and they scatter back into the wild. Cease rolling at this point.

WS2...BS0...S2...T2...W3...I3...A2...Ld5...Sv6+ 15 Points per Base Brood Size: 3-9 Cortex Leech Swarms Type: Swarm Biomorphs: Chitin, Claws and Teeth Special Rules: -Instinctive Behaviour - Feed -Fleet -Fearless -Mindless -Neural Domination -Swarms Neural Domination: Cortex Leeches do not kill their prey; they take over their bodies and turn them against their former allies. Prior to any attacks at the Cortex Leeches' Initiative step, enemy models in base contact with at least one Cortex Leech swarm must take an Initiative check. Models that fail immediately make their full base attacks (including bonuses from multiple close combat weapons, but not including bonuses from charging) against their own unit (or against themselves if they do not have a unit), and may not make any further attacks during the rest of the fight sub-phase.

8th edition[edit]

A Cortex leech swarm consists of 1-5 models which attack and attempt to take over their prey using an array of tiny claws, probing feelers and tentacles.

Name M WS BS S T W A Ld Sv Points
Cortex leech swarm 8" 5+ - 2 2 4 4 5 7+ 35


  • Helpless before the flames: Due to their tiny size, cortex leeches cannot hide from flamers and the like, making their cleansing quick and merciless.
    • Models with this rule take twice the number of hits from weapons which automatically hit their target.
  • The unseen swarm: Cortex leeches do not need to be preemptively deployed on the enemies flanks before a battle, if the hive mind wishes it simply instructs individual leeches into position mere moments before the fighting starts as at that point who is going to pay attention to such a tiny creature when there’s a carnifex on the horizon.
    • During deployment, this unit may set up more than 6” from enemy models anywhere on the battlefield.
  • Tiny and impossible to hit: Such small creatures can be obscured by the tip of an iron sight at range, making hitting them almost impossible for all but the best marksmen.
    • This model gains +3 to its armour save when in cover, and enemy units suffer a -1 to hit against this unit when shooting at it and -2 to hit when this model is in cover.
  • Surprise strike: Cortex leeches will climb up stems and tree trunks to better strike their unfortunate foes.
    • This unit hits on a 3+ during a phase in which it charged, and gains +1 to its hit rolls in the fight phase if it is in cover.
  • Instinctive behaviour: Brain leeches are the lowest of the low on the tyranid pecking order, and they know it, without the will of the hive mind to guide them the leeches will instantly flee into the surroundings, only to be picked off by the local wildlife.
    • This model must be within 36” of a SYNAPSE creature, otherwise it is instantly slain.
  • Mind slave: There are many things a guardsman will face which will want to make him flee, one of the things which are garenteed to make him flee is the sight of his comrades having worms burrow into their skulls, and then those same comrades turning on him.
    • Any model with the INFANTRY keyword which is slain by a model with this rule is not removed from the battlefield, it is set up as close to the Cortex leech unit which created it as possible. Models in this unit adjust their characteristics, move distance -2”, strength and toughness +1, ws and bs -2 (to a minimum of 6+), and suffer a -1 to their armour saves (and cannot take invulnerability saves). Any unit with the same faction keyword as the mind slave unit within 12” suffers a -1 to their leadership characteristic. In addition, mind slaved models ignore damage on a 5+ and cannot take morale tests, but lose all previous faction specific abilities.
      • Units with the NECRON or DEMON keywords can not become mind slaves, instead they hit models with this rule in melee on a 6+, as they consider them too small and insignificant to bother punching or stepping on.
  • Made for one purpose: Cortex Leeches have such tiny and simple minds that they can do nothing beyond moving, eating, hiding and attacking.
    • This model may not hold objectives.
Tyrannic Bio-Organisms
Leader Organisms: Broodlord - Hive Tyrant - Norn Queen
Swarmlord - Tyranid Warrior
Small Creatures: Gargoyle - Genestealer - Hormagaunt - Ripper - Termagant
Medium Size
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 - Mucolid Spore
Spaceborne Creatures: Tyrannocyte - Mycetic Spore - Ether-Swimming Brood
Bio-Titans: Dominatrix - Hierophant - Hydraphant - Viciator
Floral Structures: Capillary Tower - Reclamation Pool
Other Organisms: Bio-Weapons - Cortex Leech - Meiotic Spore
Spore Mine - Sporocyst - Zoats
Unique Creatures: Deathleaper - Laius Horror - Old One-Eye - The Red Terror
Auxiliaries: Genestealer Cult