Xibalban Blade (Patreon)

Weapon (longsword), very rare (requires attunement)

This toothed obsidian blade absorbs any blood that's left on it. You gain a +1 bonus to attack and damage rolls made with this magic weapon. When you hit a creature that is not a construct, plant, or undead with this sword, that creature takes an extra 1d6 necrotic damage.

If the sword has dealt necrotic damage in this way in the past hour, you can use an action to hold the sword aloft and speak its command word to summon a blood elemental, as if you had cast the conjure elemental spell. Once this property of the sword has been used, it can't be used again until the next dawn. A blood elemental uses the same statistics as a water elemental, with the following changes:

• The blood elemental has resistance to necrotic damage in addition to its other resistances.
• The blood elemental's alignment is neutral evil.

When you hit with an attack using this sword while the blood elemental is under your control and within 120 feet of you, the elemental regains a number of hit points equal to the necrotic damage dealt by the sword.

No spilled blood will go to waste.