Something as simple as 'pet' may do, but consider altering a word to fit. Such as shortening or misspelling, say the word companion, or familiar. In fact, just making the word into a proper noun (i.e., Companion a la the Firefly Series) would call it out.
So, Familiar is taken, as is Cohort. Perhaps one of these:
Companion, Pet, Summonee, The Called, Totem (+Spirit?), Guide, Meatwall (J/K), Construct (Taken. twice with Astral Construct), Homonculus (or some bastardization of same, taken), Thrall (taken), some form of the word Artifice/Artifact (Taken, kinda), Mannequin (word looks like Man-Horse, now that I think of it...sorta like clothes horse. change the 'man' part to the creature that it mimics, so Drakkequin, Felinnequin, etc.), Anima/Animus (Spirit or animating force), Guardian, Beast-(something, like thrall), Thrallbeast, Star+CritterNameHere (StarHorse, StarDragon, StarCat, etc.)
That's all the ideas that I can marginally articulate. Hope you find an inspiration.