Iggy is the second boss you’ll encounter in Paper Mario: Color Splash, and he resides in the Golden Coliseum stage. There’s a bit of a trick to this boss though, and you’ll need a special item to beat him.
First things first, when you get to the Golden Coliseum stage, check in with the shouting Shy Guy at the ticket booth. He’ll tell you that you’ve been registered for the Coliseum, so go through the door on the right and follow the hallway down to the arena.
When you enter the arena, you’ll be ambushed by a horde of enemies, but there’s a really easy way to beat them all. Turn straight around and go to the boxes behind you, there’s a Super Star hiding in one of them. Once you pick it up, you can just run right through all the enemies, and then Iggy will appear and battle you. Fight him like you would any enemy until he and his minions jump into chariots. From this point, you’re just going to need to flee battle, and return to the entrance of the Coliseum.
Now you’re going to go and get the special item, the Bone Thing Card. If you really want, you can go back to the dig site at Marmalade Valley, where the Toad at the original spot of the Bone will tell you that someone has stolen it. Turns out though, those thieves are three Shy Guys at the Coliseum, so instead just head to the door all the way to the left of the Coliseum entrance. This will take you up to the viewer stands and the bulk of the level.
It’s mostly linear, so just follow the path until you go through giant brown door that lead up to some stairs. Stop here and make sure you pick up the Ice Pick and Bottle Opener Thing Cards on your right and left, then follow the stairs up. Head out onto the ledge that has Mario shuffle sideways, then drop down the second gap. Follow that path down, and in through a window into one of the dressing rooms. Here you’ll find three members of the Yellow Toad Rescue Squad and the Bone you’ve been looking for. Squeeze the Thing Card out, and head back into the arena.
Just battle Iggy like normal, and once he and his minions jump into their chariots, wait one turn then unleash the Bone card on them. Everything after that should be easy.
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