135 From Beyond The Grave

Wolfe took the sessions with the Servants five minutes at a time but continued all night once he realized that the bond they had made with him actually changed their entire mana system.

The curse, if that's what it was, permeated their entire body. It wasn't just a mark on their necks. The more he worked on increasing their mana flow limit, the stronger the bond got, and the more their mana veins changed. 

With his efforts, they were becoming more like him, able to pass energy into their whole body and let it flow freely through them and not just channel down set pathways and into their aura to cast spells.

The amount he could draw through or push to the Servants was ten times what he could with any of the other Witches who were Bonded to him, but as he accidentally learned the first time he tried, the process left them a quivering mess on the floor.