Without a Sacrifice, a Fighter is forced to take all the damage and fight by themselves but this action is frowned upon because it shows arrogance and a questionable bond between the Sacrifice and Fighter of that team. It's expressed by Breathless that if a Fighter lives while their Sacrifice dies then the Fighter should also die, giving insight into how the bond between Fighters and Sacrifices are viewed in Seven Voices Academy. It is also considered taboo for Sacrifices and Fighters sharing different names to battle as a Unit.
Sacrifices with a destined name will have that name visible upon their body since birth, shown when Natsuo asks Ritsuka's mother whether Ritsuka had any birthmarks as a child and says it's strange that Ritsuka's destined name has not appeared on his body yet. The artificially created Zero series also possess their destined names upon their bodies, although Yamato's destined name disappeared when her bond with Kouya dissolved. There have been no cases where this has happened with non-artificial Units as of yet.
So far no Sacrifices have been shown casting Spells except for Seimei Aoyagi of Beloved. Neither have there been blank Sacrifices, however it is implied that only blank Fighters occur.
See Also: Category:Sacrifice