Ok. Is go for this:
Gods are gods because they are believed in. Your character is a god that no one believes in so has been cast out of whatever domain/heaven/plane/pantheon.
Forced to join the mortal realm he can act as his own cleric or paladin. The goal is to establish enough believers to form enough worship to read it him to the pantheon as a demigod to begin with (when he still walks the earth but is say level 18+) and then ascend to godhood full time.
I don't see night and nature cohabiting very well so I'd suggest you pick one.
But the PC would be as other PCs although I'd allow you a Feat to start off with.
So I want to create a character that is a god, pretending not to be a god. How can I make this character so that they retain some of their godly powers (They are the god of the night and can do pretty much do anything with nature)

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.