Creeping Bone

One creature grappeled by you must succeed on a Constitution saving throw or gain [roll]2d10[/roll] cumulative temporary hitpoints as plates of bone begin to grow over its skin. On each of your turns until the spell ends or you release your grapple, you can use your action to force the target to repeat this save.

While a creature has any of these temporary hit points, it is restrained. While a creature has 30 or more of these temporary hit points, it is petrified.