Some players and DM’s love the Kalashtar and all they bring to the game, but either don’t have a game in the Eberron setting or don’t want to bring all the complexity into their games. If so, the Kalasthar can be homebrewed or changed into anything you like. The quori spirit could be just a general spirit, and the evil spirits could be demons or another dark organization. After all, there are dozens of cults in D&D. You can easily create your own story that keeps all the interesting qualities of the Kalashtar but also has the flexibility to be adapted into your own campaign. Just work with your DM and you’ll get something interesting.