To Unlock: "A gift for the gifted. Ask and you will never receive."
The Demis are currently unlocked by the act of a Zeus being placed on your world. If a Dev visits and deems your world worthy he will notify you that he wants to place the avatar. Please take note that asking for the avatar is a sure way to not get it. The quote says it all.
For info on how to get a Zeus on your world go here
Those of you who previously had a Zeus on your map are probably wondering why you don't have the Demis. As said above the unlock is triggered by the act of Zeus being placed, not just that he is in your world. So in order to unlock them you will need to have Zeus placed again. For those of you who have a legit Zeus on your map you can go here
to put in a request for a Dev visit.
Demi-God: "As imagination bodies forth the forms of things unknown, the poet's pen turns them to shapes"
Demi-Goddess: "There was a world... Or was it all a dream?"
Demi-Goddess: Higher Resolution Helen Model
The Demi-Gods made their way into the 1.8 update. Special thanks to Quadraphinic for the idea. Also take note that the Helen model will not be in the game but was posted anyway for you all to see Stephen's amazing work.
All information is not final and is subject to change. If any changes are made notifications will be posted below.