The Galaxia Sword (originally from Kirby) is a powerful sword, created by the Star Spirits, that is made from the power of positive energy. It's the only thing that can shatter the Star Rod into Seven Pieces, which the Star Spirits did in Operation: GALACSIA. But as a result, the sword itself was destroyed, and could only be brought back by a strong burst of positive energy. Until then, Darkrai II held onto the sword's hilt, the only part that was there, then gave it to Nigel Uno before he left Nightmare Land. During Nigel's battle against Dimentia, just when Dimentia was on the verge of winning, Nigel's friends on Earth cheered for him, the positive energy fueling Jirachi for him to make the Golden Light Wisp, which Nigel absorbed and became his super form, which also restored the Galaxia Sword. Nigel then used the Galaxia Sword against Nega Dimentia and stabbed it right through her chest, destroying her.
In Legend of the Eight Firstborn, Meta Knight ambushed Nigel on Earth, wanting to claim the Galaxia Sword, which was "rightfully his". Meta Knight realizes that Nigel was the hero who saved Galaxia, and apologizes for attacking him. At the end of the Galactic Saga, the Galaxia Sword was used to clash against the traitorous Magolor. Dimentia fueled it with the powers of all the Wisps and vanquished Magolor. During the final showdown with Arceus, Nigel became Galaxia Nigel again and used it to battle him.