Mulmaster is one of the largest and most prominent cities in the Moonsea. It is known for being a hub of trade, particularly for the copious amount of grain produced in the Moonsea region.
It is known to be a fairly shady place, not as shady as Raven’s Bluff, but certainly high on the hive of scum and villainy scale. You know by repute that there, because of the city’s strong emphasis on trade, the Zhentarim have some presence. The extent of that is unknown to you.