Miraak is the main enemy is in Skyrim: Dragonborn
Miraak's story is as old as Solstheim itself. He served the dragons before their fall from power, as most did. A priest in their order. But unlike most, he turned against them. He made his own path, and his actions cost him dearly. The stories say he sought to claim Solstheim for himself, and the dragons destroyed him for it.