Please remember to put Fatal Frame Remake items, people, locations, etc in the Category: Deep Crimson Butterfly.

From ZeroWiki

Stone Mirror
Revives you one time only when your strength reaches zero.

This item is like an extra life. When your health has fully depleted, it will be restored to maximum capacity. This item is rarer than Herbal Medicine and Sacred Water but it can get you out of a tricky situation. Unfortunately, you can only carry one at any time, so use it wisely!