Laius Horror
The Laius Horror was yet ANOTHER Tyranid creature that was only mentioned in the fluff of 5th Edition and never received a model, given GW's faggotry made evident in the Chapterhouse debacle (and proven eternal in 2021), we will never see what it's actual model is (and not the converted Ravener shown here).
Fluff-wise, the Laius Horror was a vanguard organism in the vein of the Red Terror and Old One-Eye that came from an isolated hive ship that somehow got separated from the parent fleet and crashed into an ice world, causing events to unfold in a matter sounding a lot like the plot of The Thing. The Laius Horror somehow hides itself in the bodies of its still living victims, waiting for the right moment to get closer and strike, despite not only being a ravener-like creature, but also one that is perhaps the size of a fucking Carnifex.
TLDR; John Carpenter's The Thing as a Tyranid Arseplomancer.
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This is NOT a stub, that's all there is to know.