Spirit Cleaver

Weapon (dagger), legendary (requires attunement)

This dark metal blade can slip between a person and their spirit to sever their connection to one another. You gain a +3 bonus to attack and damage rolls made with this magic weapon, which deals 4d4 slashing damage instead of piercing damage.

While holding this weapon, you can use an action to cast the etherealness spell from it with the following changes:

• While on the Ethereal Plane, you can attack targets that you can see on the plane you originated from with the spirit cleaver. These attacks are made with advantage. If a target has 100 hit points or fewer after taking damage in this way and isn't a construct or undead, it is instantly killed.
• The spell has a duration of 1 minute, but ends early if you attack a creature on the plane you originated from with the spirit cleaver.

Once this property of the weapon has been used, it can't be used again until the next dawn.

A tisket, a tasket,
A fresh head for the basket.
A warning for my lover,
Should they dare ignore it.