Seraphim's Stiletto (Patreon)

Weapon (dagger), rare (requires attunement by a creature of good alignment)

This magic dagger is made from elven gold and a fine sliver of unicorn horn. The dagger has a pool of 20 hit points that replenishes daily at dawn. As an action, you can touch this dagger to a creature you can see within 5 feet of you and speak its command word. When you do, you can restore a number of hit points to that creature from the pool, up to the maximum amount remaining in the pool.

When you hit an undead creature with a melee attack using this dagger, you can expend a number of hit points from the pool, up to the maximum amount remaining, as part of the attack. When you do, you deal extra radiant damage to that creature equal to twice the number of hit points you expend in this way.

Unicorn horn is renowned for its healing magic. It's what made them so valuable.

The elves understood the pain of unicorns. They knew their burden. Only in death, and through the most delicate of grace, would they shave the horn from its past host. While the master rests, its magic would live on for centuries more.