Lycanthropy

Unique boon
You are cursed with lycanthropy, which can be removed by a remove curse spell. You are resistant to damage from weapons that aren't magical or silvered. In addition, you are a shapechanger and can spend an action to polymorph yourself into a hybrid of a humanoid and the animal form, or into the animal form. You retain your personality and mental stats while in either form. You have the keen smell trait in both forms (advantage on Perception checks to smell).

Werebear (brown bear)

Weretiger (tiger)

Wereboar (boar)

Werewolf (wolf)

Wererat (rat)

Your natural weapon attacks can spread the curse to creatures that fail a save (DC = 8 + proficiency + CON). On the night of a full moon, you turn into your hybrid form and lose control of yourself, giving in to your lycanthropic animal nature. Each time this happens, there is a 25% chance you permanently lose control of your character as you depart to find a pack.