Has anyone ever tried doing this with just skills, I mean, dispater has only like a +122 to sense motive, so +200 or so on bluff, diplomacy and stuff should make you able to tell him that the universe doesn't exist and he should kill himself.
Still needs to find him, although that can be done if you triangulate with some greater teleportation effect and a DC120 survival roll to find a place you've only had the description of.