This data pack adds a Mjolnir item with two abilities.
It is crafted by throwing 10 diamonds and a nether star on the ground.

Abilities you can use while wielding Mjolnir:

Ability 1: Lightning
Right-click to cast lightning on whatever you're looking at. 3 Second cooldown.

Ability 2: Thunder Blast
Sneak for 3 seconds. You will be launched into the air. When you hit the ground, up to 10 nearby hostile mobs will be struck by lightning.

Edit: I changed the Mjolnir sneak ability charging sound, which I meant to do earlier so it sounds like you're spinning the hammer.

Edit 2: I changed how the timeout works on Ability 2 so that the ability just stops after 10 seconds instead of activating. I also made it so that the ability disables if you fly with an elytra, meaning you can use it simply to launch yourself into flight.