Quote Originally Posted by martixy View Post

My contribution to stupid, but awesome is Her Serenity, The Lady of Pain.

Initially invented as a plot device. Literally as a counterpoint to all the gods, so the multiverse doesn't fall apart. Powerful enough to stand up to any old divine chap, but never leaves Sigil. Never given stats, because to do so would be to imply she can be fought and slain. Which would be ludicrous. She's the in-universe DM of the cosmology.
Seconded. In fact, in 3.5, she serves a secondary meta role for converted Planescape campaigns. Within the context of Sigil (which for most campaigns fulfills the third tenet of the Rule of Three as the Center of All) she is the narrative check against player over-optimization. There's a lot of talk on these forums of Tier 1 characters potentially breaking the game, and the potential begrudgement of DM's that act to check the warping effect.

As she stands, the Lady of Pain provides a canonical check to that, within Sigil at least. Her storyline can reference source material about Duke Rowanwood, and point out that any figure that amasses enough power to become a quasi-power gets Mazed or put in the Astal dead book. It only comes into effect if you interact in Sigil (or are worshiped there in a way that challenges her dominance), but since for most players this is a core element of narratives, it's an effective mechanism.