Governments, religions, and mages alike have often labored in discovering ways to remove the ability to cast spells from a magic user like a wizard, mage, sorcerer, enchanter, illusionist, cleric, druid or warlock and witch alike.  While many who can manipulate and control the mysterious powers of the multi-verse more than a few have been known to go against the precepts of society.  Solutions have ranged from special rooms constructed to remove the caster's connection to their source of power.  However, such means are limited when it comes to transporting the target from one place to the next.  Witch's Bindings were created to partially solve the difficulties in keeping a magic user controlled without using powerful mind altering magics themselves or completely removing the ability to see, hear, touch and use of hands from the intended target.

The Bindings are rare because they are designed to completely negate the casters ability to use spell magic.  Because of the purpose of the Bindings it takes magic to make them which the Bindings inherently try to cancel out.  Successful manufacture requires both high level craftsmanship, the best of material and a spell caster able to wield magic at least at a 5th level or higher ability.

Witch's Bindings are made from cold iron inlaid with silver runes.  Though usually taking the form of manacles that can be placed on the wrists, feet or neck of the target they can also take the form of a ring, amulet, bracelet, anklet, crown or other metallic ornamentation worn as 'jewelry' by the wearer.  Once placed on the target the bindings effectively cancel any 4th level spell or lower cast by the wearer. 

Assassins, Rogues, and Bounty Hunters have also been known to use the Bindings in their craft.  A Rogue may 'gift' a ring to a wizard who unthinking places it on their finger.  The Rogue will then ransom the spell casters own ability to cast spells back to them.  Assassins will use the item to reduce the possibility of their target or their body guard from using spells against the assassin.  Bounty Hunters similarly employ the item to simply control their bounty once captured and will often charge the cost of the Bindings to the contract in retrieving their quarry.

Key to Remove the Bindings

The Bindings have a 'Key' which will remove them from the target. If the key is lost or stolen a new one can be made, but requires 1 week of the 'new' key being physically attached to the Bindings themselves in order to work in removing the Bindings and freeing the target.

The Bindings themselves will activate with or without the Key being present once placed on the target.

Affect on Racial Spell Casting Abilities and Psionics

The Bindings do not affect 'natural'  or racial spell casting abilities.  For example a 3rd Level Tiefling Sorcerer would be unable to cast any Sorcerer Spells, however their ability to use Thaumaturgy or Hellish Rebuke are unaffected as those are racially based spell casting abilities.

The bindings have no effect on Psionics because the source of Psionic ability is internal not external like spells.

Mechanics

Spells cast using a 4th level or spell slot by the wearer have a chance of overcoming the bindings effect.  The DC equals 10 + the spell level. On a success, the caster succeeds in casting.  On a fail nothing happens.

For Ritual spells the same applies only the wearer rolls at Advantage so its DC 10 + spell level ADV.  On success the spell succeeds.  On a fail nothing happens.

Notes: Control, Utility, Cursed, Footwear, Necklace, Wristwear, Headwear, Handwear