Shackle

The Shackle is an Accessory that grants 1 point of Defense for each one equipped. It is dropped by Zombies somewhat rarely, although it's easy to acquire in plentiful amounts if you venture into the wilderness during a Blood Moon and keep killing zombies.

It can be wise to farm this Item from Zombies early on, when Defense is a hard commodity to find, and the Player has no other accessories to fill the slots anyways.

A player can only have one of this item in his accessories at a time as of the 1.0.6 update.

They become obsolete near the end-game, as the player can obtain an Obsidian Skull or Cobalt Shield, which immunity against burning blocks or knockback, respectively. They cannot be destroyed by throwing them into lava.

They can be sold to a Merchant for 3 Silver Coins.