[Seitsuki]

Spoiler for FSN possible spoilers:

In FSN, Caster made her original Master waste all his command spells but it took Rule Breaker to actually severe the Master-Servant contract (as she did to Shirou-Saber). I'm pretty sure it was explained somewhere that those command spells are just concentrated prana dumps used to evoke high magic otherwise impossible in the current world, but have nothing to do with the actual contract or Master status. Or something.