Well of Souls is a game engine and not just one world, Evergreen. There are dozens of different worlds, many of which are much better than Evergreen. Each one has different stories, classes, spells, and characters.

Each world is a different RPG game in itself. All you need to do is download it and either play it on solo mode or go onto a server that plays that world. To download another world, go to File-->"Check on-line for new worlds." Pick a world and then download the world and it'll be ready to play.

If you want to play a world that there is no server for, you can host your own server. Click here for more information on that.

Worlds I would recommend you play before leaving Well of Souls (but who says you ever have to leave!):

RoT
Athelias
Castlevania
Skavens_Plauge
Aerianell
Judgement

Just because I didn't list a world doesn't mean don't try it. I haven't played every world myself, and there are bound to be ones you like that I haven't played.

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You can make your own world, too. All worlds are 3rd party creations using the Well of Souls engine. If you want to learn how to make a world, or at least find out more about it, I have a lot of information on it here.