For witchsona week---though mine's pretty late, ahaha.
I've drawn them before but haven't posted much with them.

They're called Plague. My witch self has a scarf and fabric belt that both turn into wings and tail feathers, respectively. The plague doctor mask changes their clothing, hands and feet (once shoes are removed). They have a raven familiar who has a bit of a deformed beak, making it look like he has a horn.
They don't like people, for the most part, and produce bacteria/viruses/fungi to kill them off. Usually, they favor killing off wicked people whom enjoy causing others misery, but they cant help it if others catch the disease(s) and become infected.
They enjoy flying around and doing aerial acrobatics with their raven. The only time their mask becomes anything more than a mask is when they're in their full form (on the bottom). It can then open up, like a beak, though it mostly stays closed.
They prefer their partial form, which is the one in the middle. It's not as powerful as their full form, but it takes less energy.