Furious Storm (5e Equipment)

Weapon (any sword), very rare (requires attunement)

This magic weapon has a +2 bonus to attack and damage rolls. When you hit with an attack using this sword, the target takes an extra 1d6 lightning damage. In addition, when you are holding this sword, you can use your reaction to channel any lightning damage you take, and in doing so, you gain immunity to that attack.
Furthermore, your weapon becomes charged with lightning powers, causing it to deal an extra 2d6 lightning damage on your next melee attack.