Reliquary of Strength is found in Ishikari Plain.
Puzzle
The mountain raised the boy as her own. Demons looked away from them in fear. But the wolf watched them both, ready to provide aid.
How to Solve
The 3 statues with red demon masks must face away from the shrine toward the fire underneath. The fox without a mask must face toward the reliquary pillar. What makes this a little bit annoying is that turning one statue always turns a second one. So you must sync them up until all of them are in the correct position. Make a save before interacting with the statue for the first time. The easiest method is to not touch the unmasked fox statue at all, only spin the 3 demon mask statues.