In a Harry Potter novel, Sirius Black is a convicted murderer who escapes from this island prison in the North Sea
[DOC] [TLE] How did dementors work as the guards of Azkaban in Harry Potter ... [PAR] A Dementor is a non-being and Dark creature, considered one of the foulest to 
inhabit the world ... Harry Potter Book 3: Prisoner of Azkaban ...