Binding of the Unspoken One

Summon shadowy chains on a target in your vicinity. The target has to make a dexterity saving throw or be restrained. As long as the concentration holds, the target takes 2d8 magical bludgeoning damage. The target also must roll a D20. On a 5 or lower, the target must roll another D20 to see what limb falls off.

1-9 One of the target's legs

10-18 One of the target's arms

19-20 The target's head