Supay is something like the Criollo Devil.
Originally, supay is a demon from Inca mythology. It was the God of Death and king of the underworld.
After Europeans invaded América, catholic priest started to asociate supay to the christian devil.
This creature/god was representated in many forms: sometimes with reptilian featured (like the devil), sometimes with the head of a jaguar, with hornes, sharp teeth and tail.

In Argentina (specially in Santiago del Estero), there is a legend that says:
Supay is the lord of the underworld and it is skilled in any kind of human activity. It can be found in Salamanca, Salamanca is a place were witches and people would go to learn from supay any art or skill (usually music, art, tame, fighting, haunting, etc).
Salamanca is usually described as a cave, hidden among the heaths.

Since it can appear in any form, I draw supay as I imagine it.