thy will be done
Fans have also postulated that Rociel's relationship with the creator was a somehow sexual. I've read and reread the manga and as far as I can figure out the creator was never the benign Father watching over his creations that they worshipped in heaven. Rather, he was a wandering entity who conducted experiments in creating life, then left them to fend for themselves, never mind how screwed up they were.
When we see what Rociel's youth was like, near the end of the manga, we see that this 'god' was somewhat twisted. Rociel's love for him comes to look more like some kind of Stockholm Syndrome.