Strictly speaking, Ho-Oh's "Sacred Ash" came in two different grades.
One was the "Sacred Ash" that had a chance of being produced when Ho-Oh used "Sacred Fire" to burn away some of its own feathers, or when it used "Sacred Fire" to scorch the earth. It could revive most ordinary Pokémon and humans.
The other was a special kind of "Sacred Ash" that could only be obtained by using "Sacred Fire" to burn Ho-Oh's most important feathers as fuel—not the "Rainbow Feathers" it could scatter everywhere, but its wing and tail feathers containing the origin of its own resurrection laws.
The outrageous effects of this "Sacred Ash," put in the most straightforward, direct, simple, objective, no-beating-around-the-bush terms...
Were the Three Legendary Beasts: the first Entei, Suicune, and Raikou, who had been revived from ordinary Pokémon by Ho-Oh and leaped into becoming Legendary Pokémon, each wielding the Authority of a law.
But Cresselia's foundation was already at the Legendary Class. It did not need "Sacred Ash" to undergo such an ultimate ascension.
All it needed was the law power carried by the "Sacred Ash" as the foundation for its "resurrection."
The "New Moon Feather" was the soul, the immense "Life Energy" of the World Tree was the body, and the "Origin Power" from the Plate Fragments he had prepared was the spark that would draw resonance from the world's laws.
Together with the "Sacred Ash" as the balancing mechanism that combined those three, none of the four could be absent.
But as long as all four were gathered, accelerating Cresselia's resurrection would become possible.
Su Hao closed his eyes and used "Wave Power" to communicate with the World Tree.
"I'll find Xerneas, who possesses nearly infinite vitality, to help. Until then, I'll have to ask you to temporarily provide the 'Life