MU: Level 29 – Global – Helheim – Dark Knight
I actually leveled up not even halfway through the Dungeon by killing most mobs along the way. The Skeleton Archer gives out the most experience in the Dungeon. The Dungeon has more floors, but Sherwin can't access them yet. My Dark Knight Damage at the moment is 120-146. This has been increased by the Shadow Phantom effect. There's an NPC that gives the buff near the exits of each beginning town. This is no longer available once you reach Level 220+. If you play just a little every day you can gain some serious levels. Your character won't be disappearing anytime soon. Most MMORPGs that have been around for years are pretty much safe to play. I'd only play the English version though. No point playing international games where I can't understand the language.
Screenshot of Skeleton Archer in Dungeon:

