Devilish denizens of which we know little.
They don’t seem to have any special vulnerabilities or resistances. Many of them have aura effects and some of these are tradeoffs, increasing one thing at the sacrifice of another.
The DM posts some descriptions below…
The Danthu you saw:
These humanoids look roughly human in size, but do not have ears, and they’re nose is deeply flattened. They have many deformities on their body, made of a webby, sinuey substance, as well as several horns which have the colour and textures of a bulls horn, but shape into straight, pointed devil horns, some growing to a meter long. They wear mundane armour and weapons, but it is usually trashed and battle-worn. Various other deformities appear on their bodies, such as hook hands and enlarged eyes.
Sent by Maris.