Who?

Bael (Baal, Beal) is a King of Hell, who commands 66 legions of demons, and he controls the East (Orions). He is rumoured to harness the powers of invisibility,gaining favour, and granting knowledge. He wed the goddess Anat, also known as Astarte.

What?

His form is a three headed entity, with the head of a cat, a toad, and finally, a human. He is depicted as crawling on a set of spider legs.

When?

In the Pseudomonarchia Daemonum he is the first spirit mentioned. There are other known sources who depict him differently, such as the Livre des Esperitz where he is told to be ruling over only 6 legions.

Fun fact:

Did you know that it is almost certainly NOT a good idea to invite this fella over for a cup of tea.