Azal

Azal is the last living Dæmon who makes his only appearance in the Season 11 finale. He is normally around thirty feet tall, but he can change his size using his technology.

Role
Azal is summoned by the Masters on Weblus after they're drawn to the chaos caused by the Cyber War. They summon Azal to try and destroy Weblus and everyone else along with it. After killing Sorgat and a few Cybermen and Daleks, Azal decides to give his power to the Doctors, but they refuse. As Azal tries to kill the Doctors, Madame Vastra steps in to sacrifice herself. This confuses Azal, which turns his own power against him, causing him to self-destruct.