nWOD : Mage the Awakening
Singularity was a game I ran after realizing I wanted to create a game which allowed players to feel godlike and ultra-powerful and yet at the same time understand how much weight and responsibility that carried with it. I knew I was going to use Mage the Awakening's Arcana system to reflect their power range, but I did not want to just run a Mage game. Digging up my old notes on places like Thylea, Atlantis and the like I realized I could create a game world where all these missing or mythical lands are actually "the same land" located in the same general area in various "parallel worlds." And that these places were locales which a group of people called Walkers could easily travel to and the like.
Major sources of inspiration included Magic the Gathering's Planeswalkers, who pretty much had this sort of ability. But while Planeswalkers tended to stick the five thematic areas of Magic the Gathering, my Walkers were masters of a specific Arcana and utterly useless in another particular one.
Children's Game in Sargasso Isle
I intone the names of the Twelve Who Walk
Irkalla, Khnum, Elohim, Brahman
I summon the names of the Twelve Who Shape
Shin, Coatl, Fata Decima, Vor
I praise the names of the Twelve Who Destroy
Melek Taus, Proteus, Alpha, Omega
And I weep for the worlds the Twelve had Lost.
Later on, the players also learn of how they actually are responsible for many other events in the past, particularly the fall of Atlantis and the unfulfilled promise to migrate its stranded people to a new world. For this plot twist, I borrowed heavily from CrossGen comics' CRUX, which was written by Mark Waid and sadly was cancelled due to bankruptcy.
The game has a blog here, where many of the old coded posts are still online.