A few points for me to mention, exceptions in AoM specifically talking Norse characters for the meantime.
1/ Does Aegir have any involvement as a unit in the scenario editor?
2/ Is there possibly underwater buildings of Aegirs?
For those unfamiliar with Aegir
Quoted from source:
Germanic god of the ocean, and husband of Ran. His nine daughters, known as the "billow maidens", directed the swirling waves under his orders. He was sometimes depicted as a very old man with white hair and claw-like fingers. Whenever he left his glistening underwater palace it was with the single-minded purpose of destroying ships and their crews. To placate him the Vikings often sacrificed some prisoners before setting sail.