Has anyone else had a problem playing against a skaven player equipped with this card? From my and my friends' understanding the under empire allows a skaven player to chain destroy multiple territories fairly easily in descending order down the old world in one ruination phase (destroy one, move your army down to the next territory before it's 12 corruption is counted, repeat repeat repeat). True other players can step up to cull the herd so to speak but if they spread out their guys to fight the skaven hordes they have less warriors to defend their own territory so essentially one player has to choose to risk ruining their chance to win to stop the skaven from winning.
It seems like an incredibly broken upgrade. Maybe I'm missing something?