The Citadel of White Exile is a rocky spur located at the border where the Quasielemental+Plane+of+Mineral meets the Positive+Energy+Plane. Finder Wyvernspur was imprisoned there for some centuries.
Source: Hall of Heroes (1989)
I feel no pity for them. For light or darkness, order or chaos, our eternal reward is not determined by others. We choose our fate. They chose theirs.