★World 6 (Puzzle & Dragons: Super Mario Bros. Edition)
From the Super Mario Wiki
Special World 6, known as ★World 6 in-game, is the sixth Special World in Puzzle & Dragons: Super Mario Bros. Edition, and is a more difficult version of World 6, with brown-colored skies instead of blue. This world consists of fourteen levels and a Toad House. Roy Koopa is the boss of this Special World and is fought in his castle and airship. Clearing ★World 6- unlocks Yellow Winged Yoshi; ★World 6- unlocks Roy Koopa as an ally and the final upgrade for the Lucky ? Blocks spot at Toad Houses, where the player can have an even better chance at winning rare Skill items.
To reach the secret exit in this course, the player must first reach the branching path (where there is a signpost and a green Warp Pipe). Upon reaching the branching path, the player may notice a Gold Block in the center, between the Warp Pipe and the sign. In order to trigger the block, the player needs to clear more Dark Orbs than both Wood Orbs and Light Orbs. The course does not contain any Dark Orbs, however, so the player needs to bring an ally that can create them. Upon defeating the boss at the end of the secret path, the player unlocks ★World 6-.