The Embassy manor itself had fewer Thalmor than the other buildings which made it easy to clear the ground floor. It turns out they were strategically waiting in ambush on the second floor which caught me and Eydis off guard. With summoned daedra and atronarchs coming out of thin air Eydis got cut down pretty quick.
Welcome to hell!?
Again, my super stash of potions saved the day here - as I slowly but surely killed all the summons, summoners, guards and council members present, including head honcho Herecinde. And so all the Thalmor here were wiped out. Or so I thought.
I have no respect for my enemies.
A Thalmor maid escaped the slaughter by cowering away. I thought about sparing her but realized she might be a "bed warmer" for one of the Thalmor big wigs. Can't have any of their spawn surviving now can we? Total Ramsay Bolton moment. Go watch Game of Thrones if you don't know the reference.