Soul Magica

Soul Magica is a lighter version of Puella Magi Madoka Magica, meant to be the franchise's counterpart to the famous Neon Genesis Evangelion fanfiction "Nobody Dies." The project was first conceptualized by Chronicler-of-Soul on Deviantart and adapted into a story on AO3 by GorochuVA. The series consists of:

Changes from the original Madoka Magica include the Preservers, who serve as the "Nobody Dies" alternative to Incubators.
 * Puella Magi Madoka Magica IF
 * a Rebellion adaptation
 * Puella Magi Madoka Magica IF: The After Story
 * The Innocent Malice
 * The Tale of Jeanne d'Arc
 * a Magia Record (Arc 1) adaptation
 * an upcoming Walpurgisnacht Rising adaptation

A Magical Girl's Soul Gem, if she's made a Contract with a Preserver, does not contain her actual soul and cannot naturally taint- its color simply fades as magic is used, incapacitating her until it regains its natural color over time once it turns completely gray. However, an Incubator can "infect" a Magical Girl with a curse, and use the Gem's tie to her soul to create a Witch, similar to those that result from their own Magical Girls.