Leaden Manacles

Wondrous item, uncommon
  The stink of burnt flesh and vapours of boiling sweat waft from the wrists of the shackled spellcaster. As you watch, the creature mutters an incantation and the lead begins to glow once more. The creature lets out a pained wail, its concentration broken, its wrists seared.
  Leaden manacles behave the same as normal manacles (SRD pg.68) with the following addition: A creature that attempts to cast a spell whilst wearing the manacles must make a DC 12 spellcasting ability check. On a failed check, the spell’s magic is totally absorbed; the spell slot is expended, the action is wasted, and the manacled creature takes 1d6 fire damage per level of the spell slot expended. On a success, the creature takes half as much damage and the spell is cast successfully.
  Optional Rule: Applying Manacles. As an action you can attempt to apply manacles to the wrists or ankles of a creature you are grappling. Make a Strength (Athletics) check contested by the target’s Dexterity (Acrobatics) or Strength (Athletics). A creature with manacled wrists has disadvantage on attack rolls and can’t cast spells with somatic components. A creature with manacled ankles has its movement halved, has disadvantage on Dexterity saving throws, and attacks against them have advantage.