Hugh Hammer

Ser Hugh Hammer is an unseen character. She is long dead by the time of the series. He was a dragon-rider for Rhaenyra Targaryen's faction during the Dance of the Dragons.

Biography
Hugh was a Targaryen bastard born on the island of Dragonstone, and due to his heritage, he was one of the Dragonseeds recruited as a dragon-rider for Rhaenyra Targaryen. When the loyalists of Aegon II Targaryen marched from the Reach and besieged Tumbleton, Rhaenyra sent Hugh and Ulf the White to destroy their forces. However, the two chose instead to burn Tumbleton and Rhaenyra's garrisoned troops. Afterwards, they drank and whored with the victorious Aegon loyalists.

Reference

 * "The Dance of Dragons (Histories & Lore)"