Making a character fit for the campaign is a must, and Dark Sun is known for its limited class selection. As the player’s guide says, there are no divine classes within the world because all of the deities have either fled the world or died as part of the Dawn War.
However, I prefer story over mechanics and as such can be convinced to allow any character class type if you are able to present that you are able to play it in a reasonable and logical way as well as have a good reason for being such a thing.
As such, you will need DM permission to play a divine class. Send me an email if that is your goal with your plans and I will work with you as best as possible to ensure you have a good fleshed out character.
Additionally, only Arcane classes can Defile, unless specific rules state otherwise. (This is just part of the standard rules, expanded in the wiki page about Defiling).