Image: Rebel Wolves / Bandai NamcoOfficial screenshot from Rebel Wolves / Bandai Namco.
Feral Hunger is a hidden achievement for losing control and draining someone outside combat. It only happens at night with low vampire health, so you have to set it up on purpose.
1. Wait for night. 2. Get your vampire health low. 3. Talk to an NPC. Coen may lose control mid-conversation and drain them, which unlocks the trophy.
Save first. Guides suggest letting your health drop, then talking to a tavern innkeeper and reloading until the hunger kicks in. Avoid Closing Wounds while you try, and never test it on a character you care about.