Illithids, also known as mind flayers, are monsters with the ability to drain intelligence. Some are found in the Athkatla sewers in the Mind Flayer's Lair, in the mind flayer dungeon in the Underdark, Watcher's Keep, as well as in Sendai's Enclave. There are some offshoots, including the highly magic-resistant and spell-casting ulitharids and vampiric illithids. Umber Hulks are often found with mind flayers.