Zengyōji (善行寺) temple in the city of Kanazawa (Ishikawa prefecture) is home to the mummified head of a three-faced demon. Legend has it that a resident priest discovered the mummy in a temple storage chamber in the early 18th century. Imagine his surprise.
Nobody knows where the demon head came from, nor how or why it ended up in storage.
Note the turtle-like kappa face at back
The mummified head has two overlapping faces up front, with another one (resembling that of a kappa) situated in back. The temple puts the head on public display each year around the spring equinox.