Its an Athar PrC from Planar Handbook 3.5.
I like the flavour, it could be intetesting to see how it'd work in Sigil's setting.
Mechanics ,though, seem a bit underpowered. I thought about maybe adjusting them with DM's permission.
But thats if I get in the game, which is unlikely.
P.S.: Didn't that Tarrasque character (Gluttony) from the other Planescape game had this PrC?