Well of Souls

The Well of Souls is the source of Horance the Liche's power in Ultima VII, located in Skara Brae inside the Dark Tower. The magical well essentially imprisoned most of the souls of the people of Skara Brae (even the ones that already had been dead at the time), and Horance was using it to keep up his power level to slowly drain the souls of their energy.

In Ultima VII the Avatar first had to use the Soul Cage with the well to give it power by taking some form the souls within. Mordra admitted that this was rather brutal and heartless, but that the souls would recover from it and the sacrifice was worth it to ensure their freedom. After the Liche was destroyed, it needed the final sacrifice of a ghost to destroy the well and set the souls free.

Only after everyone else declined did mayor Forsythe do the sacrifice to atone for his error that had caused the destruction of the city, destroying the Well of Souls in the process.