Memphos is an arch devil that appears in the Island of Fire scenario in Heroes of Might and Magic III: The Restoration of Erathia.
Memphos wanted to invade and corrupt the surrounding regions. After taking up residence on a rocky, unapproachable island, he started gathering a horde of devils, planning to invade the mainland as soon as he had a large enough force.
Some elven scouts learned about Memphos' plans, and that it would take him four months to amass enough troops. The heroes of the Rampart arrived to deal with the menace, and were soon aided by a group of angels. Using some underground tunnels, their combined forces made their way to the island and defeated Memphos and his devils.