Tutorial
Drinking blood is the sole means of regaining Health in Vrakhir form. In combat, Voracious Bite steals a quick sip from an enemy; outside combat, it lets you feed on oblivious foes or neutral beasts. Blood vials from your inventory work too — assign one to a quickslot beforehand if you want it mid-fight.
Exception: on Story difficulty, you can drink directly from the inventory at any time.