Muramasa Blade

Muramasa was an immortal Japanese swordsmith who imbues his swords with his rage, madness, and hatred.

Curse
The piece of Mad Muramasa's soul embedded in every sword will slowly take over the wielder's senses, forcing them to make a Wisdom save after a certain number of kills made with this sword. The affects can be avoided by having a base Wisdom score according to the table below, or the Warrior Fighter subclass and a 10 Player level, in which case you have quadruple the amount of kills before feeling each effect.

Passive
Rending: Should the artifact or weapon not have the 'Power Immune' passive ability, this artifact can cut through it, ignoring resistances and immunities and decreases AC by 1 for every attack. If targeting a weapon, the user must succeed on a DC 15 save to not have their weapon broken.

Rend Resistant: Should the artifact come in contact with a Rending-able material or weapon, the user must succeed on a Proficiency save for it not to be broken.

Active
Reflect Types of Damage: As a reaction, you can make a 20 Dexterity check to reflect a Radiant or Force type attack back toward the attacker. They must make a Dexterity check not to take full damage. On a success, they take half damage.