Manshoon was the founder of the Zhentarim, also known as the Black Network, until he was "slain" by Fzoul Chembryl, his ally, and Lord Orgauth in 1370 DR. However, it transpired that Manshoon had created a dozen or more clones that the murderous duo then found themselves facing. Only one of these clones has survived to this day and is once more the head of the present evil organization known as the Zhentarim.

For years Manshoon was the lord of Zhentil Keep and leader of the Zhentarim. Completely fitting the archetype of the sly-tongued, sinister and decadent master spellcaster, Manshoon ruthlessly crushed revolts within his own ranks of the Black Network, easily slaughtered his rivals and weeded the weak out of the ranks of the young and ambitions by sending upstarts on nigh-impossible suicide missions. Hated and mistrusted by Fzoul, Manshoon manipulated him much as he did all others - remaining arrogant, untouchable in his power and faintly amused by it all.