Agith'maal, Tsol'teth Overlord, also known as Master Blue Dark (from Tsol'teth: agi tah'maal, "blue dark"), was a warped Tsol'teth who resided in "Anzari-tarin" - the World of Darkness, an underground realm. He commanded an army to follow him up into "Tezlari-tarin" - the World of Light, where they initiated the War of the Deeps against Seleucar, Ashtan, Shallam, and the people of Sapience in general.
He was slain by Matic Ridley, a hobgoblin defector.