Revenant's Sting

Phantom Bolts. When you fire this crossbow, the bolt becomes ghostly, passing through nonmagical cover as if it weren't there. You ignore half cover and three-quarters cover when making attacks with it.

Mark of the Hunted (3/Long Rest). When you hit a creature, you can mark it for 1 minute. While marked, the target cannot regain hit points, and your attacks against it deal an additional 1d6 necrotic damage.

Echoing Vengeance. If an enemy reduces an ally to 0 hit points, you can use your reaction to make an attack against that enemy with this crossbow. If the attack hits, it deals an additional 2d6 psychic damage.