Ok, the Story-Idea is that the Story-Author is the Dungeons-Master,
and the fans who read the story are all the Player-Character.

At the start the fans pick the Characters

Races/Species
Unicorn: What is the cutie marks ?
Dragon: What kind of dragon ?
Harpy: What bird can she change into ?
Buffalo: What is the spirit-animal ?
Zebra: What is the element of nature ?
Griffon: ... ?
Changeling: ... ?
...

Tipe
Sorcerer
Archer
Warrior/Fighter
Druid
Cleric
Medic
...

P.S. Can you also post the story here ?
http://www.fimfiction.net/group/211105/choose-your-own-story/threads