From Portals of Phereon Wiki
One of Druids special units. Requires you to fight and kill the king, open him up and grow his heart, to unlock blood magic. Recreating units with bloodmagic makes them stronger and retains some of the stats from the sacrifice. Combat wise blood fairies are self destruction units, slightly better than the explosion skill, but still high risk/high reward. The self harm is not lethal and can be healed.