We're kicking off the Infinity Guard for June! It's mostly centered around a time paradox preventing agency, which involves a bit of time travel, combat, extradimensional creatures, and paradoxes! This one was originally designed for the Cosmos compendium, but it didn't make the cut.
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This blade seems to thin to an impossible cutting edge. Each swing with it threatens to tear the very air itself. Only the most capable combatants, those as keen as the blade, know how to wield it safely and effectively.
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Infinity Edge
Weapon (dagger), very rare (requires attunement)
Vanishing Edge. You have a +2 bonus to attack and damage rolls you make with this magic weapon, and you score a critical hit on a roll of 19 or 20 with it.
Fission Wave. As an action, you can make a single straight slice in the air, creating a wave that cuts through nearly all nonmagical objects within 15 feet of you in a 90-degree arc. This slice instantly cuts through with organic material such as flesh, wood, or sponge and any soft inorganic material such as foam or nylon, provided they are not being worn or carried. The slice also creates a 3-foot deep incision in hard materials like glass or stone, a 1-foot deep incision in strong materials like metal, or a 3-inch deep incision in specially sturdy materials like adamantine, epikor, or starcore metals. Creatures in the path of this cut must also make a DC 15 Dexterity saving throw, taking 3d6 necrotic damage on a failed save or half as much on a success. You can use this property three times, and regain expended uses at dawn.