Dawn

Dawn is the ancestral sword of House Dayne. The sword's bearer is a knight of the family, who bears the title of "the Sword of the Morning".

During the reign of the Mad King, Ser Arthur Dayne of the Kingsguard bore Dawn.

Season 4
Dawn is mentioned in Ser Arthur Dayne's entry in the Book of Brothers.

In the books
In the A Song of Ice and Fire novels, Dawn was forged from the metal of a fallen star. Its blade is as pale as milkglass and is said to be just as sharp as Valyrian steel.