Ekrizdis (fl. 15th century) was a Dark Wizard of unknown nationality and the original inhabitant of the fortress of Azkaban. Alone on Azkaban's island, which was at the time uncharted by both Muggles and other wizardkind, Ekrizdis practised the worst kinds of Dark Magic and lured, tortured and killed Muggle sailors who passed the fortress. He is believed to have been insane. After Ekrizdis's death, the Concealment Charms he placed on the fortress and island faded, and the British Ministry of Magic, realising the island's existence for the first time, investigated. Other than the fact that the building was infested with Dementors, investigators refused to discuss what other evidence of Ekrizdis's activities they found within Azkaban.
- Pottermore (Mentioned only)