Waterdeep:Arcturia

Arcturia is one of Halaster Blackcloak's original seven apprentices. Rumors in Dweomercore insist that she has achieved lichdom, but when you met her at her guest lecture she looked more like an archfey.

A master of transmutation magic, Arcturia has transformed most of the Cheeky Pluckers into various animal-headed forms. The one exception is Danny Elfman, who had his arms removed, but now has hands growing from his temples.

You've also learned that she enjoys creating mimics, and has a certain fondness for her mentor, Halaster.

Arcturiadoom

As the name implies, the entirety of the 14th floor of Undermountain is Arcturia's lair. The name also lends credence to the Dweomercore rumors that she is a lich, as a "-doom" is a lich's lair.