Ninja Gaiden IIEdit
The Jade mask is found in the Amazonian Jungle in South America. While it looks like the Mayan type of mask from Palenque, its origin predates that, and theories of its origin lead to one pyramid called the "Necromantale". The Pyramid of the Necromantale was believed to have been hidden in the jungle with this mask, but some have thought that it disintegrated are collapsed to rubble over the millennia.
It does not appear in Ninja Gaiden Sigma 2, as the door it would normally unlock will open when all nearby enemies are killed.