You were fighting Tessa, and after you eventually defeat her by decapitating her with her own sword. You notice that she gets back up after a few minutes and reattaches her own head before removing her helmet, showing Cyn's yellow Cross Eyes as she rushes at Doll and feasts on her to heal

Cyn: Going Absolutely Ravenous On Doll

Doll: Screaming In Agony As Her Ribcage Gets Torn Open