Nexus: The Kingdom of the Winds, whose original Korean title is Baran, is a 2-D Suikoden-looking MMORPG with a historical/fantasy kingdom theme.
It's easy to get in and learn how to play but, like Othello, is hard to master. You can choose from one of four classes and then, once you hit level 13, it becomes a completely different game. Quests are no longer given to you (befriend an archon to find new stuff to do, basically), new skills and tasks are no longer explained, and there's no limit to leveling up since every 4 months, a new "elite" stat group is created so once-noobs can be considered noobs again. Before the "Renewed Earth" redesign, it wasn't as much a home for elitists and 13 year olds who trap you in Vale (the PK area you can't avoid for too long). However, it is still addictive. Every now and then, a Korean dude will play on the US servers and shout at you to "give itam!"
Guy 1: I was playing NexusTK earlier and someone stole all my green squirrel pelts!
Guy 2: You only need one of those, you know.