——"Command Seals."
This is a power or mark that typically only those masters capable of controlling, summoning, and commanding servants to fight for them can possess.
Its essence is a crystallization of Magic Power, a symbol of the master's identity, and also a resource that can be consumed.
Under normal circumstances, each master will have three strokes of Command Seals. Each time a Command Seal is consumed, one can complete the strengthening, healing, summoning, or even forceful obedience of a servant through a "command" method.
As long as it is within the master's capability, they can use Command Seals to make servants do things that are normally impossible, including but not limited to space transfer and other matters close to the Magic Domain, or even command their suicide.
The master of Chaldea, Reiger, once met Fujimaru Ritsuka in the Fairy Country of Britain, but they seldom communicated. Fujimaru Ritsuka possessed Command Seals, engraved on the back of his hand.
