With only a few in existence, these bone bows are blessed by the reaper god, Ashus. It helps some of his selected reapers to deliver death upon those that try to avoid it.
One of these bows found itself in the treasure pile of the illithilich Xaniv the Whisperer, from which it was picked up by Sif of the Phoenix Nebula. While she was not a devout follower of Ashus, it never felt like that the god of death objected to her use of it.
simple ranged weapon, 1d6 piercing, 80/320 ft, two-handed, shortbow, very rare (requires attunement)
This bow is blessed by the god of death, Ashus. Holding this bow marks you as one of his reapers. You gain a +2 bonus to attack and damage rolls made with this magic weapon. On a hit, the weapon deals an extra 2d6 force damage.
Reaper. This bow creates infinite spectral arrows when you draw it, and these arrows can cut through to the Ethereal Realm and hit creatures through the planes. In addition, since you do not need to draw physical arrows, you can make one attack with it as a bonus action on each of your turns.