Last month, Trion Worlds temporarily made its most recent expansion free, due to a naming conflict with a children’s charity. The free weekend apparently went so well that Trion’s decided to make the change permanent.
Prophecy of Ahnket (formerly Starfall Prophecy) is now free to all Rift players. The move comes in anticipation of the next update, Celestial Storm, which will be coming to the game next month and will also be free. That update will add a new overland zone, quests, raid rifts, and four primalist souls when it launches on July 19.
You can dig into the lore of the update and learn more about all its features on the Rift site.