Mjolnir Type Weapon for Thor Cleric

Hey fellow DMs, I'm working toward the conclusion of a background story arc of one of my PCs who is invading the temple of Thor (where she grew up and was ousted). The BBG has a hammer similar to Mjolnir, and should they kill him, she will get the item. I'd like your thoughts on whether it's a bad-ass enough item (it's the end of a background story arc, it needs to be bad-ass) and if it's too under/overpowered. The weapon is cursed by a nearby aboleth, which is part of the story arc.

Mjolnir

Warhammer +1, Cursed

This hammer flashes with arcs of electricity.

Upon a hit, lightning springs from the hammer and delivers a shock to the creature. The target takes an additional 2d8 lightning damage and it can't take reactions until the start of its next turn. Additionally, a bolt of lightning arcs toward as many as three other targets within 15 feet of the first target. The targets must make a dexterity saving throw (DC 14) and take 2d8 lightning damage on a failed save, or half as much on a successful one.

Cursed: This hammer is cursed, and becoming attuned to it extends the curse to you. As long as you remain cursed, you are unwilling to part with the hammer, keeping it within reach at all times. While attuned to this weapon, you have disadvantage on attack rolls made with weapons other than this one.

In addition, at dawn the owner must make a DC 7 Wisdom saving throw. On a failed save, the owner develops piscine properties which becomes more severe with additional failed saves. After 8 failed saves, the owner is under the psychic control of an aboleth. The curse can be removed if the aboleth is killed, sent back to the plane of water, or remove curse is cast on the hammer.