D&D 5th: Ravenloft
The bullywugs are portrayed as a violent race of marsh-dwelling frog-like humanoids.
“a batrachian race of bipedal monsters which inhabit wet places – rainy forests, marshes, damp caves or virtually any other place which is shady or dark and has water nearby, for bullywugs need to dampen their skins from time to time.”
Bullywugs are described as evil and are thought to be rapid swimmers, with an attack routine that combines a hopping charge with an impaling weapon to deal extra damage to opponents.
It is also said that they have the chameleon-like power to alter their skin-colouration to different shades of grey, green, and brown, so that they can hide and attack from surprise.