CMF 35 Progression Chart - United States Army

army slotConjure Undead Army is a Necromancy ability. It is unlocked from the seventh tier of talents, requiring 35,000 souls in the Well of Souls. It conjures up to four spirits in the same way asI can't summon it using undead army? as in the 4th slot to add it is locked out. I can't find anything on the that points me in the rht direction.