Brontide

One young girl used to fear the storms that raged just outside her window. Each flash of lightning startled her, the constant pounding of the rain gave her chills, and the thunder deafened her. She hated storms. That is, until her imagination allowed her to see the storms for how they really were: the result of benevolent creatures making a ruckus.
Now the scary sounds come from friendly sources, and she realizes there's nothing to be afraid of. Only when the giants come to seek her help to prevent dark creatures from coming to her world is she brought back to her fearful reality. How much of it is her imagination, and how much is real?