Easter eggs in Heroes.

Apparently, yes, because it says that it appears somewhere after 100 Thunderbirds. Read the thread further and do fun things in the editor.

I didn't even have 30, and it appeared. I didn't even have time to fight the demon. The alien has an ability like that (I don't know for sure if all Warlocks have it) - after the enemy uses any spell, it is added to a "blacklist" and cannot be used again. And the specialization is "Sovereign".