Leftover Command Spells

Refers to the numerous command spells that line Risei’s right arm. If a loser of a Holy Grail War drops out with command spells still remaining, the command spells are collected. These leftover command spells are stored by the supervisor of the war. The leftover command spells are locked by the Holy Word, and thus cannot be taken or stolen by force. The leftover command spells can be used to perform magecraft without any elemental affinity, and therefore can be thought of as a pseudo magic crest. Although the command spells are consumed when used, Kirei possess no magic crest of his own, so they are useful for him to supplement his capacity as a magus.

Fate/Zero Animation Guide II: Glossary of the holy grail war II