Magical Prison
From Populous Wiki
Magical Prisons are buildings which cannot be built. They can contain Shamans and have to be rescued by other followers to cast spells again.
Your Shaman is trapped in a Charma prison on Level 15: Incarcerated and on a Undiscovered Worlds Level : Prisons. You also have their Shaman in a prison on this level.
You can also have Prisons on multiplayer.