Source: Dungeons and Dragons - Honor Among Thieves

Wondrous Item, legendary (requires attunement by a Sorcerer, Warlock, or Wizard)

Resembling a small dragon’s horn, this arcane device glows with a hellish internal light when held. As an action while holding this horn, you can invoke a necromantic effect called the Beckoning Death.

The Beckoning Death arrives at the start of your next turn and manifests as a crimson cloud of smoke that fills a 30-foot-radius sphere centered on the horn. The sphere doesn’t move with the horn. At the start of each of your turns, the sphere’s radius increases by 30 feet. The cloud disappears after 10 minutes or when your concentration on the effect ends. Any creature (including you) that has 9 or fewer hit points when it ends its turn in the cloud is slain by the Beckoning Death. A Humanoid killed in this way instantly transforms into a zombie (see the Monster Manual). The zombie obeys the commands of the horn’s creator, the lich Szass Tam.

Once you use the horn’s property, it can’t be used again for 1 year.