The Necro Sword came to me while I was building characters for a new campaign. I kept building variations on hexblades, and or taking a dip in hexblade, and for whatever reason couldn’t get myself to build anything but a hexblade. So, play a hexblade you say? I can’t always play a hexblade, and besides, most of the other features didn’t fit. Just the cool sword.
Wondrous item, legendary (requires attunement)
This black blade is made of pure shadow and can take the form of a dagger, rapier, longsword, or greatsword at the wielder’s discretion. Changing forms is a bonus action and you must be touching the weapon to do so. The weapon can be summoned back to your hand with a bonus action, so long as you are attuned to it, regardless of distance or barriers between you.
When you strike a living creature with the Necroblade, you gain temporary hit points equal to your proficiency bonus. When you slay a living creature, the Necroblade gains a cumulative +1 bonus to damage. After a minute without striking a creature, this bonus returns to zero.
The Necroblade hungers for slaughter. Each day, you must slay a living creature (at least as big as a rabbit) per month you’ve been in possession of the sword (minimum 1). If you fail to do so, at midnight you make a charisma saving throw. The DC is 10+1 per creature you were to have slain. If you fail this saving throw, the blade takes control for the next 24 hours, and will ensure it gets the souls the next day. The save is made each day regardless of whether or not you passed the previous day you fail to slay enough creatures, and the DC does not reset after you do. As such, long term possession of the blade is very risky.