• How did the Gods become mortals? → Basically, they wanted to become mortals. It was their choice to become mortal. They picked the body, and altered things to make their lives make sense to the mortals.
• How long have the Gods been in the mortal bodies? → Unlike other games, the Gods weren't reborn as mortals, living their mortals lives since birth. The have been in those motal bodies for about 4 years now. So yes, some of the Gods might have to go through high school.
• How exactly did the Gods get their bodies? → They had two ways: Either they created one, like they did in the past (imagine they have like an empty human body they could use whenver they wanted). Or they could take over a human (as in a living breathing person with a life and a family and friends) and "posses" them for as long as they want. Please note that most Gods would choose the former over the latter, it's just less complicated.
• Do they still have all their memories? Do they still remember all they did and their relationships with each others? → Yes, they do. They remember EVERYTHING.
• Do the Gods still have their powers? If they do, how much power do they have as humans? → They still have their powers, but on a much lower level. Zeus won't be able to throw thunderbotls nor Ares will cause great wars in the middle of the campus. It's more like a strong power of suggestion: Ares will still be able to make people fight each other with a very skilled art of manipulation, Eros can spread love and lust with some charm, etc
• Do you humans know about the Gods? → No. They are not aware that they are living among gods and goddesses. They just think this is normal college life.
• Are the humans normal humans like you and me or the humans from the myths? → Some are normal and average humans, but others are the spirts of those humans like Achilles or Hector. The Gods chose them to join them in their mortal lives, to make things a little more interesting and fun. We'll only be accepting 14 myth-human (7 females, 7 males), so they balance the other 14 normal humans.
• The humans from the myths, how did they get their human body? → Since they died centuries ago, they are only spirits and have no power to choose a mortal body like the Gods do. That's why they are the only ones that are reborn humans (that and because the Gods thought it would be fun to make them suffer a little bit having to grow as humans again).
• How exactly does the Greek System work? → Everything is explained here.
If you have any more questions, please comment here.