Galacta Knight is a powerful warrior who was sealed away due to his power that is summoned by Meta Knight, and is the final boss of the "Meta Knightmare" mode in the video game Kirby Super Star Ultra. Galacta Knight is also the penultimate boss of the "True Arena" mode, where he fights Kirby as well.
Galacta Knight reappears in Kirby's Return to Dreamland in the "True Arena". Other than that, Galacta Knight has no impact on the story, but is speculated to be the one who told Magolor of Kirby's exploits.