House Costayne of the Three Towers is an old house of the southern Reach, sworn to the Hightowers of Oldtown. Their seat stands upon a cliff above the southern shore of Whispering Sound, where the sound runs out to meet the Redwyne Straits — a watchful place set athwart the sea-lanes between the Arbor and the Honeywine. The Costaynes blazon their arms quartered: silver chalice and black rose, black field and gold.
Lord Tommen Costayne sat at the Three Towers in the latter years of Aegon the Unworthy, and the line has held the cliff and the cup ever since without much trouble or much glory. At the opening of A Game of Thrones House Costayne keeps its place among the lesser bannermen of Oldtown, content to drink from a silver cup and watch its roses bloom black against the sea.