The Humanarium.

Could you kill your god to win your freedom?
When humanity was defeated by the aliens there was no bloodshed. One alien was all it took to capture everyone who landed on their planet. A thousand foot tall and with superior technology, we stood no chance.
Thousands of years later humanity has been thrown back into the dark ages and we live as pets to the alien. Trapped inside a terrarium, religion has become the way of life, praising the god that feeds us and steals us away, seemingly at random. One man refuses to believe the world is only as big as the four walls that surround him and by a twist of fate he discovers a way beyond the glass. But is he ready to face the titanic world and huge creatures that lie outside?