Call to the Grave is the Rivadis Empire's Ultimate Power in Takeover. It converts two random enemy squads on the map to a Rivadis Empire squad. The squads converted will become the Rivadis Empire counterparts to the squads. For example, a converted melee infantry squad will become the melee infantry squad counterpart of the Rivadis Empire. Upon being converted, the squads lose all their abilities (including being Veterans or Elites) and gain the abilities of their Rivadis Empire counterparts.
The type of the Rivadis Empire squad will depend on the squad the Rivadis Empire can produce. For example, if a range squad is converted, it will become an Undying Archer unless the Rivadis Empire can produce Skeleton Archers. Avatars become Undying Assassins or Shades upon conversion. Trebuchets and Poison Catapults can not be converted.