[Variant] Howl of the Storm - D&D5e (Patreon)

This magic item is forged from a fragment of a blue dragon's horn, adorned with intricately carved runes that channel its immense power into a resounding, thunderous roar. Once per day, as an action, you can blow the horn to evocate a turbulent storm in a 30-foot radius around you. The tempest churns with fierce winds and dark storm clouds blot out the sky overhead. The storm rages for 1 minute, making the entire area difficult terrain. The bearer of the Howl of the Storm remains untouched by its effects.

While the storm is active, you can use a bonus action to unleash the following effect:

Lightning Strike. You command a bolt of lightning to strike a point of your choosing within the storm's area. Each creature within 5 feet of the point must make a DC 13 Dexterity saving throw. Those who fail are blasted by the intense electrical surge, taking 2d10 lightning damage. Those who succeed manage to evade the worst of it, taking only half damage.