A Practical Guide to Evil is amazing and one of the few webfics out there on par with The Wandering Inn, but I would't really call it a progression fantasy - viewed in LitRPG terms, it's a very rules-light system. If you're Named, you hew to either Above (good) or Below (bad), you have three words representing things you can do exceptionally well, and you become both bound and empowered by stories. This idea gets used to its absolute fullest, and the viewpoint character becomes a master of the craft - on the surface something might look like a truce negotiation between armies, while actually being a pitched battle between the Named on each side for control of the narrative. It's also got great representation. There's a roughly equal gender balance, most characters are non-white, and queer characters are disproportionately well-represented including a very prominent (and wonderful) ace character.

In terms of background and history, the evil empire of Praes has traditionally been run according to the good old principles of demon-summoning and flying fortresses and sentient tiger armies, since when you're empowered by stories these ideas can work... at least in the short term, since in the stories Evil always loses in the end. The Black Knight and his band of Calamities took that personally - "half the world turned into a prop for the glory of the other half". He and Empress Maleficient took over and started running things more rationally, doing things like looking at orcs as people with the capacity to be terrifying shock troops rather than as random cannon fodder to be thrown away in their hordes, and specifically avoiding all the stories that lead to eventual defeat. They were able to take over the stereotypical Good Fantasy Kingdom of Callow, Praes' traditional arch-nemesis. The protagonist grew up in Callow after the takeover, in one of the many orphanages set up by the Black Knight - orphaned children being a classic source of heroes - and her ambition is to join the Legions of Terror and effect change from within. In the first chapter of the story, apparently by happenstance she comes under the Black Knight's tutelage, and things go from there.

Also, it would be remiss of me not to mention that it's now finished(!) and the author is working on another story, Pale Lights. It's early days yet, but so far it's shaping up even better.