Source: Explorer's Guide to Wildemount

Wondrous item, legendary (requires attunement)

A Stormgirdle is a wide belt made of thick leather branded with the symbol of Kord. The girdle's clasps are made from dragon ivory.

Dormant. While wearing the Stormgirdle in its dormant state, you have resistance to lightning damage and thunder damage, and your Strength score becomes 21 if it isn't already 21 or higher. In addition, you can use an action to become a Storm Avatar for 1 minute, gaining the following benefits for the duration:

• You have immunity to lightning damage and thunder damage.
• When you hit with a weapon attack that normally deals bludgeoning damage, it deals thunder damage instead. When you hit with a weapon attack that normally deals piercing or slashing damage, it deals lightning damage instead.
• As a bonus action, you can choose one creature you can see within 30 feet of you to be struck by lightning. The target must make a DC 15 Dexterity saving throw, taking 3d6 lightning damage on a failed save, or half as much damage on a successful one.

Once you use the girdle's Storm Avatar property, that property can't be used again until the next dawn.

Awakened. While wearing the Stormgirdle in its awakened state, you gain the following benefits:

• Your Strength score becomes 23 if it isn't already 23 or higher.
• Your Storm Avatar's lightning strike deals 4d6 lightning damage (instead of 3d6).
• While transformed into a Storm Avatar, you gain a flying speed of 30 feet and can hover.

Exalted. While wearing the Stormgirdle in its exalted state, you gain the following benefits:

• Your Strength score becomes 25 if it isn't already 25 or higher.
• Your Storm Avatar's lightning strike deals 5d6 lightning damage (instead of 3d6).
• You can cast the Control Weather spell from the girdle. This property can't be used again until the next dawn.