Maelys Blackfyre

"All the same, his descendants continued to threaten the Targaryens until half a century later, when Barristan the Bold slew Maelys the Monstrous on the Stepstones, extinguishing Daemon's line."

- Varys

Maelys Blackfyre is an unseen character in Game of Thrones. He is not expected to appear in the series, being long dead by the time it begins.

Biography
Maelys Blackfyre was the last in the male line of House Blackfyre. Like previous Blackfyres before him, he made a claim for the Iron Throne, which led to the War of the Ninepenny Kings. This conflict ended when Maelys was killed on the Stepstones by Barristan Selmy, extinguishing Daemon Blackfyre's line and ending further threat of Blackfyre pretenders.

In the books
In the A Song of Ice and Fire novels, Maelys Blackfyre was the last male descendant Daemon Blackfyre. He had a huge upper body and a second head sprouting from his neck. This was said to be the head of his twin whom he had eaten in the womb, earning him the nickname "Maelys the Monstrous", as he had become a kinslayer, though not by choice.

Maelys was named Captain-General of the Golden Company after killing his cousin Daemon when they fought for the position, becoming a kinslayer by choice. During the War of the Ninepenny Kings, Maelys was one of the Band of Nine, a group of merchants, sellswords and pirates who joined forces to carve kingdoms out for themselves. After conquering the Disputed Lands, Tyrosh and the Stepstones, Maelys convinced the other members of the band to attack Westeros and aid him in retaking what he claimed was his birthright. However, the Targaryens acted swiftly and sent their own force out to the Stepstones to meet him. There, Maelys was slain by Ser Barristan Selmy in single combat on the Stepstones, ending the Blackfyre pretensions to the Iron Throne.