As with most bosses, leaping on Dimentio's head is the key to victory. But make sure to attack from below with Luigi's super-jump, then try to hit him again on your way back down.

The series continued with Paper Mario: The Thousand-Year Door on the ... it'll be near the door you enter this screen from. Super Dimentio Card 48 8–4. Move all the way to the room in which ...

After you beat all 100 of the samurai type guys you unlock 6 or 7 super rare cards. They are Mario's teammates from Paper Mario: The Thousand Year Old Door.