Potion of Bloodlust

A berserking potion out of Carl's own silver Pacifist's Box: doubled strength and movement speed, halved dexterity and constitution, a stacking speed bonus for every kill landed while it's active, and a debuff that strips away any sense of where the drinker is or why they're fighting. Mordecai says he's seen it wipe out half a party before and warns Carl not to touch it; Carl agrees and puts both doses away unused.