With "The Fall of X" in full swing, revelations regarding the Age of Krakoa have been arriving fast and furiously. None of these secrets have been more stunning than what unfolded at the end of Immortal X-Men #18 when fans learned that the original Mr. Sinister, Nathaniel Essex, had achieved his long-pursued dream of Dominionhood.
Source:https://www.cbr.com/x-men-five-forms-of-sinister-ranked/