World 6 (Puzzle & Dragons: Super Mario Bros. Edition)
From the Super Mario Wiki
World 6 is the sixth world in Puzzle & Dragons: Super Mario Bros. Edition. This world takes place in the sky, resembling that of World 7 from New Super Mario Bros. Wii, with a remixed version of the world theme from that game. Like other worlds in the game, Orbs are scattered about the map. This world consists of fourteen levels and a Toad House. Roy Koopa is the boss of this world and is fought in his castle and airship. Clearing World 6- unlocks Red Yoshi, World 6- unlocks Light-blue Yoshi, and clearing World 6- unlocks Flying Squirrel Mario and Flying Squirrel Luigi as Leaders and the Awaken spot at Toad Houses.
A more difficult version of World 6 exists as a Special World: ★World 6.
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 Water Orbs than both Wood Orbs and Light Orbs. The course does not contain any Water 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-.