Maelys Blackfyre, better known as Maelys the Monstrous, was called "the Monstrous" in part due to his freakishly large size and strength, but also due to the fact that he had a small vestigial second head sprouting out of the side of his neck - the remnant of a twin that he had absorbed in the womb. Maelys was the fifth and last Blackfyre Pretender to rebel against the Targaryen dynasty. Maelys Blackfyre was the last of the Blackfyre Pretenders to the Iron Throne. Like previous members of House
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