"Each Servant is kept in this world by a sympathetic link to his or her Master," Signum proceeds. "Masters also often provide supporting magic, though if you cannot, I will not be offended. As Archer, I am completely capable of acting on my own - ah, that's right."

Chastising herself briefly for skipping an important part, she adds, "Each Heroic Spirit summoned for the war is one of seven classes - Archer, Berserker, Caster, Saber, Lancer, Rider, and Assassin. I believe the names are self-explanatory. In every Grail War, there is one of each, each summoned by his or her own Master."

"Back to the subject of fighting, I will protect my life with yours - in fact, with some exceptions, Servants cannot exist without their Masters. This makes killing the other Masters a viable strategy for victory, and it makes your protection the very most important part of my present existence, even without my honor and oaths at stake."

Signum looks at Hayate, worried and small-looking in that wheeled chair of hers - her legs were most certainly crippled entirely - and decides to withhold the full benefits of her Independent Action ability. If this innocent little girl was killed because of the Grail War...well, there was hardly any point in succeeding without her even though she very well could. A world where that could happen wasn't worth wishing on.