Forgotten Realms: Girdle of the Storm for D&D 5E

In my Forgotten Realms game, I'm creating some magic items to seed my campaign with:

Only one of Talos' Stormcallers, in each generation, are granted the knowledge to craft a Girdle of the Storm. The Girdle's powers return to the Stormlord upon his chosen's death. It is a secret weapon that Talos guards closely.

GIRDLE OF THE STORM
Wondrous item, legendary (requires attunement by a cleric with the tempest divine domain)

You gain these benefits while wearing the girdle:

• You may use your Wrath Of The Storm feature 2 additional times.

• Wrath Of the Storm's damage increases to 2d10.

• When you use your Wrath Of the Storm feature you gain resistance to lightning or thunder damage (your choice) for 1 minute.