Command Spells

Command spells provide a Master with three absolute commands that can be used on their Servant. Command spells are indispensable to ensure the obedience of a Servant. Considered to be a Servant’s shackles. Over the course of a Holy Grail War, command spells can be used up to three times to compel Servants with an undefiable command. Depending on how they are used, command spells can empower a Servant to exceed its normal strength or capabilities. However, after using it for the 3rd time, the command spell will be lost.

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

Reiju. Command Spells.
They are proof that someone is a Master. They provide a Master with three absolute commands that can be used on their Servant.
When all three have been have been used up (or taken) the magi loses their qualification as a Master and is eliminated by Moon Cell.
However, there are a few special circumstances and exceptions:

  • A Master has no more command spells, but their Servant still remains.
  • A Master has defeated their set opponent on the current level.
  • The battles on the next level have not yet begun (before the announcement of a Master’s next opponent).

Depending on these, Moon Cell will put off elimination.
Even if you use up all your command spells in the battle arena, as long as you immediately supplement them before leaving the area, you’ll be spared from Moon Cell’s punishment.

Fate/EXTRA Material: Encyclopedia of Fate/EXTRA