Well everybody knows about the Greek/Roman gods, right? Well that's what my story is based on, having the Greek gods involved in the story setting. They are supposed to be these high and mighty warriors who cannot die most of the time, and control the weather. Well what if in my story, there is something that exists among the stars that is much stronger? Something that has a vast power? Something to threaten the human and other races mentioned in the story? Would it seem interesting, to keep all the qualities of the Greek gods but to invent people/creature/society that has more power? and can take them down easier? Cause in my story there is lots of alternate beings who have alot more power then Zeus himself. One of my female characters takes the role as Overlander, as she fights Demons/Crime/ Disasters and keeps the balance to the Earth. She has much more power then Zeus, and has lived immortally for several thousand years. I just thought i could express my story idea bit where fellow members can get a glimpse of what it really is.
You could borrow from another mythology, or the same e.g the Titans. What about some colosal celestial being (dragon, humanoid whatever) the size of planet or something?
Titans are gods, they just aren't Olympians. Just to let you know in advance- Titans are NOT more powerful than the Olympians. The Olympians did win the war, after all. Zeus is technically the most powerful god. Having a higher being would only make sense if you made it so one was created. They can come from nowhere in Greek Mythology, as Gaia came from nowhere and Uranus came from Gaia even though she had no partner. Gods have also come from places like cut off genitalia or foreheads for presumably no reason.
I'd just like to point out that the title "Overlander" has been used in Suzanne Collins' "Gregor the Overlander" series. To answer your question though, perhaps something like one of Lovecraft's creatures? (Btw, I love your avatar of Katniss Everdeen - I hope the movie is good!)
Humans are more powerful than any god, Because a gods power stems from the belief of humans, stop believing in Gods, they cease to exist. Therefore making a Gods ultimate weakness Alzheimer's disease or amnesia. On another note. Zues's Parents Chronos lived among the stars and was overthrown by Zues, you could just make a higher tier of god plotting revenge on Zues. Maybe his Uncle =P
Seeking approval? A story concept means nothing. I can tell you now, it has all been done before. What matters is how you write it, the characterization, the flow, the imagery, all of it. There's no benefit in asking what other people think of the concept! They'll either say,"Sounds great," or, "it sounds like a ripoff of..." If the idea stirs you, write it. Then ask people what they think of the final story. After they tell you what they don't like about it, revise it, usually several times, until you're happy with it or until you throw up your hands and say the hell with it. Please read What is Plot Creation and Development?
Hmm, I like the idea of titans, they after all were the parents of Zeus, but were overthrown by him and his brothers, Hades and the sea god. It could be that there were more of them, and they don't like their fellow uber gods being locked away by those cheeky upstart children. Of course there's always the question, where did the titans come from? Grandparent gods? Cheers.