Prerequisite: Dwarf
You never forget, and never forgive. Those who have wronged you in the past know this too well.
As a reaction to a friendly creature you can see taking damage, you can hold a grudge against the attacker. Until the attacker dies, you have +1 to Damage rolls (from weapons or spells) against creatures which you hold a grudge against.
Grudges have infinite duration unless you forgive a grudged creature during your daily preparations. You may only forgive one creature per day this way. You cannot hold multiple grudges against the same creature, and you can only hold as many grudges as your level.