Dear scared of the consequences,
You'll be happy to know that it's all right! God doesn't mind stories about other worlds or superpowers. I mean, one of the best Christian books is about kids going to another world and helping to save it. That book is called Narnia. You might want to read it.
God is ok with stories about other worlds and powers; it's the content He is concerned about. If you story is about kids going to another world and getting powers like healing, fire, ice, wind, light, stopping time, and stuff like that to save that world or something, that's ok. If your story is kids using satanic powers to go to a world of darkness and hate, God would have a problem with that. Whatever you do is fine, what matters is the meaning, the content, and the way you do it. If your story is about kids going to another world and saving it but the methods are bad, like satanic stuff, then there's a problem.
So, stories about other worlds and power are fine. I even write stories like that. Just watch out for how you do it.
Your sister in Christ,
God's servant.