Horned Rat
The Horned Rat is the festering disgusting god of the equally disgusting Skaven race in the Warhammer Fantasy setting.
Spreader of AIDS and STIs, rolling around in his own muck, the Horned Rat only exists to troll his own worshippers and the rest of the world and to tear down civilization, the arts, anything remotely good and replace it with his own favourite pastimes (namely disease, backstabbing, and cruelly toying with others).
As you can expect, no one likes him and he is the archenemy of several gods, particular Sigmar and Sotek. The only reason he hasn't been curve stomped and fumigated is because he has perhaps more worshippers alive then any other god in the setting and this gives him a blotted amount of power (and a needless sense of self-importance). Granted each individual skaven isn't worth squat but put enough together and it gives him enough power to be a major god of the underworld.
However, he doesn't do anything, as he is too busy getting eaten by Sotek or his head smashed in by Sigmar's hammer.
Once his divine majesty deigned to make an appearance, to end one of the civil wars that was tearing his people apart. Summoned by the Grey Seers, he ate a few skaven, gave them a telling off, ate a few more and then left some pillars of warpstone behind with instructions on how to backstab and bitch better in his name. And no word of him since them.
The Horned Rat keeps going on about a great plan to take over the world and passes it onto his Grey Seers for them to tell the masses but this is really just a tool to keep the Skaven in line and generally striving towards the Rabid Cat's goals. Needless to say, once (if) the Skaven do take over the world, then the Horned Rat will swoop in, thank them for their hard work and then eat them all, satisfied he has finally won (just as planned).
He has his own greater daemons, the Vermin Lords, who are renowned trollers who give any skaven and others quite rightly the creeps. It is one of the toughest units a Skaven force can wield, combining powerful magic, strong combat skills and general unpleasantness into one hideously glorious model.
Considering his perchance for scheming he is probs Tzeentch's pet rat that got too much of an ego boost and decide to go it alone. Although equally possible with his connection to disease he is Nurgle's test subject and is taking out his pain through others.
Should you see a Horned Rat in your area, call your local fumigators to get rid of the problem. Nothing ruins a day like a nasty ratmen infestion.