Basically, yeah, when the Heartless reach the keyhole, they devour the heart, and the world where the keyhole is, fades from existence. Also, you can't put such powers on yourself, Wolfa. When a keyhole is locked with a keyblade, it can not be opened again. With any keyblade, not just yours.
Ped finally stepped towards the keyhole. He summoned Oathkeeper, and directed its tip towards the door. As he did, the keyblade's tip started spewing sparkles everywhere, little white dots flying around, circles of pure light forming and flowing around the keyblade, and suddenly, there was a big flash, and a picture of a crown appeared under Ped's feet. He was still in the same position, now rays and circles of light flowing all around him, finally so thick that everything was white, but only for a moment. It soon turned into clouds. Dark blue, dark sepia, black clouds. The place seemed to have clouds beneath his feet too, as he realized what he stood on didn't look like a floor. Before him, about 3 meters from the level he was standing, was a ball of light, which suddenly also flashed, and shot a beam into the sky, shortly stopping, and forming a huge keyhole in the sky.
Ped swinged in circles with his keyblade a bit, and then turned it towards the keyhole. He had no idea what he had to do before when he found the keyblade, but it almost seemed like he someone knew what to do. Like he had done it before, but he knew he hadn't. He also remembered flashbacks when he first raised his keyblade towards the keyhole, but he only remembered the fact that he had flashbacks. The content of them was erased from his memory.
A thin outline of light started appearing around his keyblade's tip, and as soon as it reached the other end, where it started and formed a full circle, the circle started decreasing in size, until it was the width of the keyblade's tip, and at that exact moment, a ray of light flew very fast into the keyhole, the keyhole starting to glow more, and more brightly, with beams of light playfully dancing in their separate directions, until it was again pure light everywhere. Then, where Ped was before, was what came before him. He was still in the same position he was when the ray of light shot into the keyhole, and he lowered his keyblade.
He took a calm, long breath in and out, and turned around, towards his companions.
"Well, heh, I guess that we'll have no problem with this keyhole any more," he said, summoning a half-smile.