Elevator pitch

Doireann is a kind of nature spirit referred to as raven lords/ladies because of them usually taking the form of unusually large ravens. People used to make up stories about them being raven nobility. This is not even remotely true, but the name stuck.

They have the gift of prophecy. They can also to some extent tell if someone is telling the truth. 

If you can throw a golden chain around their neck while they are in flight, they will be bound to serve you, and they lose the ability to speak anything but the truth.