Grand Spiky Shell
From the Super Mario Wiki
A Grand Spiky Shell (also known as Grand Bowser's Shell in the European English version) is a Skill Item in Puzzle & Dragons: Super Mario Bros. Edition. It raises the Skill levels of teammates whose Skill levels have reached level 4 using Bowser's Shells such as all Magikoopa types (and their evolved forms), Boom Boom, the Koopalings (and their evolved forms), Bowser Jr.; all three forms of Bowser, and Rock Luigi. Grand Spiky Shells can be obtained by opening up ? Blocks; winning them from the Lucky ? Blocks game in Toad Houses; or from defeating Boom Boom in World 8- with a 10+ Combo attack.