One of Britain's Thirteen Treasures, King Arthur's llen or mantle is said to make anyone underneath it invisible, though able to see out (Harry Potter, anyone?). This item is known from two sources, the prose tales Culhwch and Olwen (c. 1100) and The Dream of Rhonabwy (early 13th century).
In Culhwch Arthur's mantle is included in the list of the only things Arthur will not give to the protagonist Culhwch, but it is not named specifically or otherwise described. However, the names of several of the other items contain the element gwyn, meaning "white; sacred; blessed", suggesting otherworldly connections for the whole list. In The Dream of Rhonabwy, the mantle is specifically named Gwenn, and has properties analogous to those given in the lists of the Thirteen Treasures, though here it is those on top of the mantle who are made invisible.
In Culhwch Arthur's mantle is included in the list of the only things Arthur will not give to the protagonist Culhwch, but it is not named specifically or otherwise described. However, the names of several of the other items contain the element gwyn, meaning "white; sacred; blessed", suggesting otherworldly connections for the whole list. In The Dream of Rhonabwy, the mantle is specifically named Gwenn, and has properties analogous to those given in the lists of the Thirteen Treasures, though here it is those on top of the mantle who are made invisible.
~Ally