He was a vital component of Smithy's invasion of Mushroom World. Exor, on his descent to Bowser's Keep, shattered the Star Road, breaking off seven Star Pieces, thus eliminating the power of wishes from the world. Exor crashes into Bowser's Keep, sending Mario, Bowser, and Toadstool (who were battling in the castle) flying to other regions of the world. The keep is occupied by the Smithy Gang, and is used as Smithy's base of operations on Mushroom World.
At the start, a message appears saying: The eye is protecting Exor! And you must beat one of his eyes first because, if you atack Exor, no damage you will deal. After beating one of his eyes you are able to atack Exor, the best form to beat him instantaneously is to use the Geno´s Whirl, if you do it correctly, it can do 9999 to Exor, the maximun damage of the game, beating it once for all. The Neosquid (or mouth) doesn´t protect Exor, but it atacks, too, like the eyes.