Necromancer – “Assassination of the Ruler” [Campaign 3, Mission 4]

I immediately downloaded one perk (it seems like "Eternal Slavery") and after each battle, skeletons and skeleton archers come to me! I built up an awesome army there... (30 dragons, ... I don't remember who else, and about 6,000 skeleton archers). I easily defeated Cyrus! (I got about 300 archers for each titan!)