Hide of the Feral Guardian

From Explorer's Guide to Wildemount, pages 271-272.

Description
Armor (studded leather), artifact (requires attunement).

It is believed that this polished and beautifully detailed leather armor was a gift from Melora, bestowed on a long-forgotten archdruid and champion of the natural world before the terrors of the Calamity.

Dormant. While wearing the armor in its dormant state, you gain the following benefits:
 * The armor grants you a +1 bonus to AC.
 * While you are transformed by an effect that replaces any of your game statistics with those of another creature, you have a +1 bonus to melee attack and damage rolls, and you retain the benefits of this armor.
 * As an action, you can use the armor to cast Polymorph on yourself, transforming into a giant owl while retaining your Intelligence, Wisdom, and Charisma scores. This property can't be used again until the next dawn.

Awakened. When the armor reaches an awakened state, it gains the following properties:
 * The AC bonus of the armor increases to +2.
 * While you are transformed by an effect that replaces any of your game statistics with those of another creature, your bonus to melee attack and damage rolls increases by 1 (to +2).
 * When you cast the Polymorph spell using this armor, you can transform into a cave bear (use polar bear statistics).

Exalted. When the armor reaches an exalted state, it gains the following properties:
 * The AC bonus of the armor increases to +3.
 * While you are transformed by an effect that replaces any of your game statistics with those of another creature, your bonus to melee attack and damage rolls increases by 1 (to +3).
 * When you cast the Polymorph spell using this armor, you can transform into a guardian wolf.