Bead of Exsanguination

This small, black bead measures 3/4 of an inch in diameter and weights an ounce. Typically, 1d4 + 1 beads of exsanguination are found together. When thrown, the bead absorbs hit points from creatures near its impact site, damaging them. A bead can store up to 50 hit points at a time. When found, a bead contains 2d10 stored hit points. You can use an action to throw the bead up to 60 feet. Each creature within a 20-foot radius of where the bead landed must make a DC 15 Constitution saving throw, taking 3d6 necrotic damage on a failed save, or half as much damage on a successful one. The bead stores hit points equal to the necrotic damage dealt. The bead turns from black to crimson the more hit points are stored in it. If the bead absorbs 50 hit points or more, it explodes and is destroyed. Each creature within a 20-foot radius of the bead when it explodes must make a DC 15 Dexterity saving throw, taking 6d6 necrotic damage on a failed save, or half as much damage on a successful one. If you are holding the bead, you can use a bonus action to determine if the bead is below or above half its maximum stored hit points. If you hold and study the bead over the course of 1 hour, which can be done during a short rest, you know exactly how many hit points are stored in the bead.