[Sabriel pauses, hesitating. And then, slowly, she speaks, trying at first to give Kazuma the context for what happened.]

Kerrigor- a powerful Dead creature was using his body to anchor himself to Life, so that no matter how many times he was defeated and driven into Death, he'd always come back.

My cousins- learned the location of his body. So we- went there, to try to dig it up and destroy it, to break is connection to Life and a great part of his power with it.

It was in an ensorcelled coffin. We couldn't get it open with the mages we had with us, and night was coming on fast. But we were close to the school.

[And they'd needed some place defensible, and more mages to help with the opening spell.]