Perhaps one of the oddest animals outside of The Maw is the squid. The image is the only testament to the creature's existence. The absence of the two suckered tentacles that typify squid and cuttlefish is probably an error on the part of the illustrator; nevertheless it does prove the existence of squid in the Thief World.
Notes[]
I could tell you where it is, but that would spoil all the fun...
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The squid is seen through a porthole in the briefing slideshow for Kidnap, where Garrett was stowed away on the Cetus Amicus