A heavily-modified World of Warcraft which removes the concept of classes, allowing the player to pick-and-choose abilities to create their own unique character. Another server has a random selection+choice concept which is very fun.
Has various challenge modes and the ability to rework a character back to level one for a reward.
While lacking some bits and pieces of convenience, it's really quite good. Has some expensive pay-to-win. It's ultimately not good because it has bonus experience available to all the players so there's no actual authentic world, it's just a bunch of overpowered characters smashing through everything; fail. Or play it single-player if you'd like..