dark mind
The true antagonist and final boss of Kirby and the Amazing Mirror. He shows himself after Kirby defeats Dark Meta Knight a second time. With help from Meta Knight and Shadow Kirby, Kirby is able to defeat the dark tyrant with ease.
His resemblence to Nightmare and Zero suggests that he may be a counterpart to Nightmare, Dark Matter, or both. Void's ability to mimic him supports this theory.
He is implied to have survived his defeat at Kirby's hands and may have been responsible for Queen Sectonia's corruption and the appearance of King D. Mind.