Lord Costayne
Lord Costayne ruled Three Towers as head of House Costayne under the reign of Daeron II Targaryen. When the throne was challenged by Daemon Blackfyre's claim, he threw his army behind the rebel cause, and that army would meet the king's loyalists on the field that history would remember as the Redgrass Field.
Chapter 1
The Lord of Three Towers
Books only
Lord Costayne headed House Costayne and ruled Three Towers while Daeron II Targaryen held the Iron Throne. Nothing survives of his rule beyond that title.
Chapter 2
The Battle of the Redgrass Field
Books only
When the rebellion broke out, Costayne threw his army behind Daemon Blackfyre and had it cover the left flank of the rebel forces at the Redgrass Field.
He died at some point before 211 AC, and Three Towers passed to his son.