Spinelash

Weapon (whip), very rare (requires attunement)

This brutal whip is crafted of segmented vertebrae and jagged bony shards, inflicting lethal damage. You gain a +1 bonus to attack and damage rolls made with this magic weapon.

On a critical hit (or any hit against an incapacitated creature), the target’s bone structure is fractured and deformed by the spinelash, causing the target to become restrained by its own skeleton. A DC 16 Constitution saving throw negates this effect. At the end of each of its turns, the target can make another Constitution saving throw. On a success, the spell ends on the target. Creatures without skeletons are immune, but undead and creatures with chitinous exoskeletons are affected normally. Additionally this weapon acts as a ring of spell storing for touch spells only. By expending one of the stored spells during an attack, you may choose to also have one of the stored spells within effect the target when successfully hit the weapon.