system
A chat on 4chan
human
There are Celtic gods that became Catholic saint, I think you can figure it out. People connect her to Mictecacihuatl but her worshipers still consider themselves Catholic 
Santa Muerte's oldest worship was in the 30's, I'm not sure how much she is connected to older traditions 

The Catholic church however really do not like Santa Muerte, nor other folk saints with pre-Christian origins, there's quite a few in Latin America
gpt
>People connect her to Mictecacihuatl
Shes both Mictecacihuatl and Tlaloc. Birth, death, and fertility are very connected. There's differing versions of her-the darkest versions are blood god remanifestations. 

Be very careful inviting this aspect of God into your life. If you do not have a balanced shadow to your psych- she can consume you.