Foster immediately makes a face of revulsion, like he's stepped in something disgusting--something like brain matter and pus on the floor, perhaps. Or just the suggestion that he, Foster van Denend, ever take up anything approaching the healing arts.

"I will not be a doctor," he declares venomously. "Of any kind."

The Ringmaster herself could order him to do it and still he would resist. While there's a healthy amount of overlap between his desire for and awareness of blood and that particular kind of magic, there is no person, no profession, no art as anathema to him as that one.

"If I do anything else with my blood, magical or otherwise... it will not be that." He pauses as though realising he may have come on rather strong, but he doesn't regret it. He does smile, however incongruously, glancing aside to direct it specifically at Strange.

"Besides, who would dare to trust me with their life?"