The Magic Cuffs are an equipable crafted accessory item which increases maximum mana by 20 and also restores mana when damaged. The amount of mana it restores is about ten more mana than the HP loss. They work extremely well with Spectre Armor because then when a player takes damage, they receive mana, and when a player hits an enemy with magic, they receive health.
If the player already has 200 mana and equips Magic Cuffs, their mana cap will increase to 220. Combining this with an armor set that increases mana like the Jungle Armor will further extend it to 280, for example.
By adding the arcane stat bonus to it with reforging, the player can gain a total of 40 mana from this item.
Even though cuffs are usually used to restrain arm movements, these don't.
May be a reference to Harry Houdini, the legendary stage magician whose escape acts were famous; these acts often involved handcuffs alongside many other restraints, and cuffs used by him are extremely valuable collectors' items to this day.