Spike Shield

Spike Shield is a badge in Paper Mario and Paper Mario: The Thousand-Year Door. In Paper Mario, it is found in Dry Dry Ruins, in the second of the three Pokey Mummy coffins in the first room. In Paper Mario: The Thousand-Year Door, it is found in Rogueport Sewers, in a room with spikes that can only be passed with Yoshi or Vivian. If equipped by Mario, he is able to jump on any enemy with a spiked head, spiked helmet, or upward-facing spear without taking any damage in return. The badge also allows Mario to safely use his hammer on enemies with front-pointing spiky defenses, such as Spear Guys in Paper Mario, and Bristles and Cortez's sword and sabre in Paper Mario: The Thousand-Year Door. Mario's attacks act as they would with any other enemy.

Merluvlee's prediction in Paper Mario

 * "I see...a Spike Shield Badge. Right after you enter the ruin, you see three coffins aligned in a room. The Badge is in the middle coffin."