Howl of the Storm - D&D5e (Patreon)

Wondrous Item, rare (requires attunement)

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 60-foot radius around you. The tempest churns with fierce winds that pick up and toss aside unattended small objects, and dark storm clouds blot out the sky overhead. The storm rages for 10 minutes, 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 one of the following effects:

Raging Gust. All creatures within the storm's radius must make a DC 16 Strength saving throw. Those who fail are swept off their feet by the tempest's fury, taking 2d6 bludgeoning damage and being knocked prone. Those who succeed brace themselves against the storm, taking only half the damage and remaining upright.

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 16 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.