Ampami RPG is a story-driven RPG server with what I would call quite a complex story. The server currently has 2/4 chapters complete, and is actively being worked on.
The story happens soon after the defeat of Krulp (The leader of a rebellious necromancer group). The world regenerates after the attack, rebuilding damaged areas and restarting stopped conflicts. But, as things start going back to normal, a dire prophecy is made, that another threat of similar scale is coming...
Server contains custom mobs and items, both optional and required quests, and a pretty big map to explore, with more coming in future chapters. While the story may be quite linear, the many side quests and possible exploration you can do nullify the story's linearity. Of course, this is optional, so if you prefer a linear story you can stick to it.