is it the ghost standing in front of the moveable tree near dampe's house with the ghini's. Because she is laterally standing in front of the secret passage and she wants the ghini's gone.
that is one of my favorite games, but give me a sec and ill edit this post with my riddle
Edit:
game:FSA
I hide in the heaviest place. You cant go on without me. But i can only be found with power. The fire it burns but where im at it doesnt matter
all im going to say is it is a person and that is it since their are only a couple of fire ridden levels it shouldnt be hard to figure out. And i edited it to hopefully make the power part a little clearer