Pyramid Stone
From the Super Mario Wiki
The Pyramid Stone.
Pyramid Stone is a stone shaped like a triangle in Paper Mario. Along with the Diamond Stone and the Lunar Stone, Mario and his friends need this stone to gain access to Tutankoopa's tomb in the Dry Dry Ruins.
It can be found in a secret chamber, guarded by two Stone Chomps. It fits into the first Chomp Rock statue.
