Manshoon is a powerful evil wizard in the Forgotten Realms setting.
Manshoon is the founder of the Zhentarim and was once ruler of the black network, but was overthrown and killed by Fzoul Chembryl in a coup.
As Fzoul prepared to face a clone of Manshoon upon his death, he discovered that a dozen of clones had in fact awakened. This spawned the "Manshoon wars" as each clone was programmed to destroy the other ones. To this day, only 3 clones subsist, having overcome their impulse. The one who has rejoined the Zhentarim (under the orders of Chembryl) is considered the true Manshoon.
He is the archetype of the evil overlord: extremely intelligent, ruthless and manipulative. He seems satisfied to be under the orders of Fzoul and to focus on his schemes to further the influence of the black network without having to suffer the day-to-day administration.
Manshoon is an extremely dangerous adversary to have as he has full access to the ressources of the Zhentarim and, if necessary, is an epic-level wizard.