It's made from wood with what seems to be real teeth. Can post more pictures if needed.
here is my guess from reverse image search.
This mask is one of the devils used in "La Pastorela", a traditional play about the shepherds who are told of the the birth of Christ and the triumph of the God's angels over Satan's diablos.
https://www.britishmuseum.org/collection/object/E_Am1990-08-260