House Dayne was loyal to House Targaryen during Robert's Rebellion. Its most famous member was Ser Arthur Dayne, the Sword of the Morning, one of the most honest and true knights. He was killed by Lord Eddard Stark and his men when they stormed the Tower of Joy to find Lyanna Stark.
Edric Dayne is the current head of House Dayne. He squired for Beric Dondarrion, who is betrothed to his aunt, Allyria Dayne. The greatsword of House Dayne is named Dawn and was forged out of the core of a fallen star. It is said that only the most worthy of knights of the House Dayne can wield Dawn, thus receiving the honorific title 'Sword of the Morning'. Dawn had not been wielded since the death of Ser Arthur. It is presumed to be stored somewhere in Starfall.