Mudman

Mudmen (also spelled "mud-men") were monsters that spontaneously formed in pools of mud where large amounts of magical auras were concentrated.

Locations
In Calimshan, underneath the second falls of Two Falls River, so many magic items had been dropped by people trying to cross the muddy and slippery path under the falls that mudmen began defending the items.

The largest collection of mudmen in Faerûn had formed in the Bay of Chessenta. North of the city of Soorenar, at least forty had formed, with still more than that reported along the Akanamere. Other mudmen "colonies" were found south of Unthalass, in the Alamber Sea north of Delgora, east of Lyrabar, in Starmantle Bay west of Amry, and spread in isolated spots within the Easting Reach.

Rumors & Legends
Some sages believed that if powerful magical artifacts were left unfound for long enough periods of time in watery environments, they would inevitably form larger and larger mudmen to defend them. Twelve-foot-tall and even fifteen-foot-tall mudmen had even been reported in the Raging Reef!