"We didn't notice anything until we saw the blood dripping around us, and looked up. That’s where we found what was left of the missing Astropath, and the thing that was eating him."
- — Deck Officer Severine Pyle, 24th Deck Command, The Light of Calixis
A Thornmaw is a truly bizarre-looking alien entity. Its bulk is a rough teardrop shape and seems to lack an outer skin, formed instead of dense masses of exposed muscle and sinew. The upper half of the monster is heavily covered with projecting spikes and spines that get larger and thicker the further up the body they go. Atop the body is a crown-like arrangement of six to eight large curving horns upon which are often displayed assorted trophies, usually the remains of previous kills.
On the bottom of the body is a dripping mouth filled with grinding teeth and surrounded by clusters of menacing, armoured talons. The Thornmaw uses these grasping limbs to snatch up its prey and draw them into its mouth, where it rends them into easily devoured gobbets of flesh.
Anatomy and Physiology
While the Koronus Expanse has only seen very isolated encounters with this being, reports indicate a Thornmaw seems to wait with unnerving stillness as it readies itself for attack. With the mouth closed and the talons gone limp, while extremely distinctive, its appearance is still not so unnatural that the true danger is apparent. Indeed, given the incredible nature of many of the other denizens of the Expanse, on two occasions a Thornmaw was taken for some sort of alien plant life whist it was resting on native foliage. While it can move with speed when pursuing prey, it seems to conserve this mobility until necessary.
Thus, a Thornmaw may simply float slowly in the air, and those seeing it for the first time often simply dismiss it as just another strange but non-aggressive alien lifeform unless they take extra care to scrutinise it closely or maintain the properly alert readiness necessary for survival in the Expanse. Once it is ready, though, the Thornmaw slowly descends, seeking to ambush its victims while they are unaware.
However, other Thornmaws have been reported to hide themselves away, secreting themselves amidst the branches of tall trees, near the ceilings of shadowy rooms, or the upper gantries of a voidship's cargo bays. Once out of sight, it seems to prefer to wait and snatch up lone individuals in their tentacles and devour them. Given the few numbers of encounters, however, it is very possible the creature may exhibit other patterns of behaviour in other situations.
Seen up close, a Thornmaw reveals its true essence. The tiny but malevolent eyes spaced between the clusters of tentacles indicate its predatory nature, as well as the talons themselves, which when extended appear as segments of razor-sharp chitin and bone. The Thornmaw tends to use these to snatch up and entrap its victims, flensing away skin in preparation for feeding.
Worse yet, the Thornmaw has enough limbs to engage several enemies at once; one encounter reports the creature was able to ensnare one individual while lashing out at anyone else brave enough to try and rescue him. It is also able to impale enemies on its collection of horns, and some incidents have noted past remains still affixed to the thing's body as grisly mementoes of past feedings.
The prey, once entangled by the powerful limbs and subdued by the attack, is then devoured in thin grinding bites, usually head first. Some explorers of the Expanse related grisly tales of Thornmaws having even been known to dismember their victims slowly, snipping off limbs bit by bit before going in for the final kill. The sudden and unexpected way it attacks, along with the horrifically painful nature of its feeding manner, leads many to believe it also feeds on the prey's psychically-released terror and agony, perhaps even more so than the actual flesh consumed.
There have only been isolated encounters with this creature in the Koronus Expanse, most prevalent along regions of calm Warp tides. This, along with the widespread locations reported (including aboard starships travelling through the Warp), lead some Imperial savants to believe it may indeed use hidden passages through what the xenos call the Webway to travel throughout the void.
The first and most infamous of these tales is from the freighter Light of Calixis, where it appears only a few score Thornmaws slowly moved through the ship, leaving bloody remnants of unlucky crew in their wake. Despite aggressive searches that managed to kill off a few of the beings, and even the venting of some compartments to the void, the foul things managed to devour everything in their path. The final communications reveal the extent of the terror, with search parties falling prey to the beasts as they sought out their missing compatriots.
Only a few crewmen survived in a single saviour pod, luckily found on the outskirts of Lucin's Breath, with wild tales of dangling arms that ripped apart bodies and awful maws that bit through skulls with terrible ease. Since then, there have only been a handful of incidents, for which many a Rogue Trader has given praise to the God-Emperor.
Calixian spire nobles with a penchant for xenos collectibles and always eager for the latest and rarest of finds have already created a demand for huge thorns and bony tentacle lengths, and Cold Traders have made small fortunes crafting clever fakes to satisfy their endless desires for grotesque novelty.
- Rogue Trader: The Koronus Bestiary (RPG), pg. 31