Once a powerful demon-prince, who commanded favours from monarchs and sorcerers all across the ancient world, Zdexiphos has fallen from its former “grace.” In its original, physical form, it is a floating mass of horns, tongues, tentacles, mouths and other orifices, with a single right arm. It's lone hand sports six fingers.
At home in the abyss, it rules over a fortress of confusion and nausea, where every passageway causes vertigo and the pull of gravity is different in every room. Zdexiphos feeds off this confusion and disorientation, fattening its alien body on the madness it causes in humans.
But it fell afoul of its betters and was punished. Belial marched his armies out against Lilith on the Plains of Hallucinations and Zdexiphos sent them falling off the Edge of Madness into the fiery forges of Dis. As if in mockery of the fall from grace, Belial's legions fell from the sky into vats of molten metal and liquid ghosts, destroyed completely. Zdexiphos revelled in this creative use of its ability to change the gravity of its own confusing domains, but the dark lord Belial was not amused.
For two centuries Belial plotted, allowing Zdexiphos to rise in power, to annex surrounding domains and defeat weaker rivals. And then Belial placed the Doors of Perception where Zdexiphos could get them. The bait was seized upon and the trap was sprung. An agreement was signed by seven arch-fiends of the abyss and Belial had his revenge. Zdexiphos was cursed to inhabit the form of an ordinary, domesticated cat — and not for a temporary length of time, but in perpetuity. It can escape, of course, so many things are possible for demons, but it must now rely on human sorcerers and their propensity to take animals and demons as familiars. It has been this pained for a long, long time now.