>The Sacred Ash (Japanese: せいなるはい Sacred Ash) is a healing item found in most games since Generation II. Unlike other items in general—which work on only one Pokémon—the Sacred Ash, when used, is used on multiple Pokémon at a time. It can only be used outside of battle. - Bulbapedia
It is basically a max revive for every Pokemon in your party. Also only Ho-oh holds this item when encountering it
