Steelsilk Mantle
Wondrous Item,
Rare
(requires attunement; cost 5000 gp)
Crafting Components
Silk of a giant spider
This ornate purple silk cloak is interwoven with enchanted steel threads. As a bonus action, you can reshape some part of the cloak into any mundane steel object that can be held in one hand, such as a sword, a key, or a cage. This item detaches from the main cloak, but can be reattached on your turn (no action required). Only one item may be detached from the cloak at a time. Three times between long rests , when you see a creature target you with an attack you can use your reaction to spin the cloak into its path. The cloak hardens like a shield, increasing your AC by +4 against that attack.
Source