From A Wiki of Ice and Fire
An undergaoler is a dungeon overseer.
In the Red Keep, there are supposed to be six undergaolers, but currently there are only three. Each undergaoler commands over gaolers and turnkeys, answering to the chief undergaoler in turn.
- Rugen, an undergaoler in the Red Keep since the time of King Aerys II Targaryen. Actually a cover identity of Varys. Oversees the black cells.
- ↑ 1.0 1.1 A Feast for Crows, Chapter 8, Jaime I.