Oversway: You sure you don't mean one of the Death themes, like Ashen Empire? I never see the AI pick Broken Empire. Then again, I've never made the mistake to let the AI play Ermor after the last time...
Perhaps one out of five times the AI will pick BE. You can allways recreate until he does to force him.
I have played several SP with undead Ermor. You could play it on a smaller map around 70 provs or have it as a race to get victory points before Ermor does.