Carnifex

The Carnifex is a monstrous Tyranid organism that is used as a living tank by the hive fleets. It is armed with the most advanced Tyranid Bio-Weapons and is used primarily as a shock trooper to carry out starship boarding actions, frontal shock assaults on entrenched positions and for besieging fortified locations or enemy armour formations. As Tyranids are constantly evolving their forces, many different species of the Carnifex exist. However, all Carnifex share some common characteristics: they are very large creatures, standing significantly larger than a man; they have a thick carapace, which provides excellent protection from damage, and they frequently use some of the heavier bio-mutations utilized by the Tyranids, such as Thornback Armour, a Barbed Strangler, Spore Cysts, a Venom Cannon, or the ability to project burning Bio-Plasma.

Variants
There are four variants of the original Carnifex, which are: In addition, there is a powerful Carnifex wandering the universe by the name of Old One Eye, infamous for having survived many battles thanks to its ability to regenerate from most wounds, something a normal Carnifex cannot do. This beast has also displayed the ability to operate - and actually command swarms of “orphaned” Tyranids from well outside the reach of the Hive Mind, something which has caused those who know of it great concern.
 * Thornback - The thornback bears genetic enhancements that resemble large spikes or thorns, and are commonly used to breach enemy lines.
 * Screamer-Killer - Screamer-Killers are easily identified by the piercing shriek that got it the "Screamer" part of its name. This scream is a warning for attackers that the Screamer-Killer is about to launch a blast of Bio-Plasma.
 * Bile Beast - The Bile Beast spews acidic fluids onto its foes before attacking in close combat using its huge crab-like claws.
 * Stone-Crusher - The Stone-Crusher is a siege variant of the carnifex. Armed with huge crushing claws, capable of tearing down the thickest walls, a massive scything tail and battering rams, it is used for crashing into enemy ranks and fortresses.