Quote from : Dreams of Gods & Monsters Book

I...I sang," she whispered, "if that matters," and Karou felt her heart pulled to pieces. This Misbegotten warrior, fiercest of them all, had crouched in an icy stream bed to sing a chimera soul into her canteen, because she hadn't known what else to do. The singing wouldn't have mattered, but she wasn't going to tell Liraz that. If Ziri's soul was in that canteen, Karou would happily learn whatever song Liraz had sung and make it part of her resurrection ritual forever, just so that the angel would never feel that she'd been foolish.