Deciding to question Matthais before you go any further, you head to the abbot's quarters.
"Basileios," says Matthais as you enter the room. "I didn't expect to see you back here. What can I do for you?"
"You have some Iceborn locked in a cage," you tell him. "I spoke to them, and they told me that you intend to sacrifice them to the Eight. What's more, I think I saw it happening, with a man called Geraint—I was there when you performed that ritual in the tower."
"Those Iceborn were trying to kill us," explains Matthais. "It's just as well we spotted them as they were scaling the wall. Yes, we are sending them into the service of the Eight, something that the Brothers themselves do willingly as part of the compact that ensures the survival of both ourselves and the legacy of our culture. It is no more than you yourself are doing, surely?"