Mjölnir (5e Equipment)
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Weapon (light hammer), legendary (requires attunement)
As an action, you can channel the might of Thor. A churning storm cloud forms, centered on you and spreading to a radius of 360 feet. Lightning flashes, thunder booms, and strong winds roar. Each creature within the cloud when it appears must make a Dexterity saving throw. On a failed save, a creature takes takes 10d8 lightning damage (or half as much damage on a successful one) and becomes deafened for 5 minutes.
You create a bolt of lightning that arcs toward a target of your choice that you can see within range. Three bolts then leap from that target to as many as three other targets, each of which must be within 30 feet of the first target. A target can be a creature or an object and can be targeted by only one of the bolts.
Each round you maintain concentration, the storm produces different effects on your turn.
First, gusts and freezing rain assail the area under the cloud. The area becomes difficult terrain and is heavily obscured. Each creature there takes 1d6 cold damage. Ranged weapon attacks in the area are impossible. The wind and rain count as a severe distraction for the purposes of maintaining concentration on spells. Finally, gusts of strong wind (ranging from 20 to 50 miles per hour) automatically disperse fog, mists, and similar phenomena in the area, whether mundane or magical.
Second, hailstones rain down from the cloud. Each creature under the cloud takes 2d6 bludgeoning damage.
Third, you call six bolts of lightning from the cloud to strike six creatures or objects of your choice beneath the cloud. A given creature or object can't be struck by more than one bolt. A struck creature must make a Dexterity saving throw. The creature takes 10d6 lightning damage on a failed save, or half as much damage on a successful one.