[Well, he can't say he's surprised. He takes a breath and sighs it out, opting to go for the short version of the explanation.]

It's because of how things work in my world. Long story very short, acting against my nature in a big way can corrupt my magic. I'm a healer; I don't like the idea of testing a power that can kill people on anyone...even if they volunteer.

[It's been a weird day.]