Yojimbo Onslaught (5e Equipment)
From D&D Wiki
Weapon (katana), very rare (requires attunement)
This katana was made from the essence of a powerful warrior who's lost there life on the battlefield and was turn into a spirit which was only thought to be a myth. Legend say that a piece of yojimbo soul was infuesd with the sword giving it great with a heavy cost.
Ragnarok: The soul of yojimbo seek battle when in uses small cut can become a deadly attack if your not careful. Make a melee spell attack with this weapon against a creature you can reach. This melee spell attack has a +9 bonus to hit, and upon hitting, the target takes 2d10 necrotic damage. Those hit take 1 necrotic damage at the start of their turn for each time they are hit with this effect. The maximum necrotic damage a creature can take from this effect at the start of your turn is equal to your proficiency bonus. The necrotic damage taken at the start of the creature's turn stops when the target receives healing, or when a Medicine check to close their wounds succeeds against DC. Your DC for this is 8 + your proficiency bonus + your Wisdom modifier.
Zantetsuken: Before you make a melee attack with this weapon, you may choice to make an all powerful attack. This attack deals 5d10 additional slashing damage. The weapon regains use of this effect at dusk.