In my earlier concepts Enigma Beast was a form that Laistrygon could take (he's a shapeshifter, largely taking forms of various animals), but it became more of something of a remote body that explores arcane realms that Laistrygon cannot. It is likely the embodiment of something very ancient (what with resembling an early mammal). It also has a mind of its own, though it does tend to follow Laistrygon's bidding, being an extension of his mind.

I suppose EB is a familiar of sorts but I'm not entirely certain if it'd be the right word!