What happens after you get the 7 treasures in mystery dungeon?

After collecting all seven treasures, you return to the Great Glacier, find the door hidden in the ice and descend to the lowest floor. You meet Mew, who says that the treasures should make you whole, and that you should feel the full power within yourself. If you still have open treasure slots in your inventory, you will automatically receive the remaining treasures you don't have yet to fill them.