Can *Gift of Furious Might* be used on Rising Heat of Stone and Sand to increase the damage from *Gift of Searing Heat*?

Can Gift of Furious Might be used on Rising Heat of Stone and Sand to increase the damage from Gift of Searing Heat?

Yes. Gift of Furious Might lets a Spirit boost the Damage of one of its Powers by +3. Gift of Searing Heat is one of Rising Heat's Powers (even though it's working with/through another Spirit) so it qualifies.