So I am in MB and just entered Chelsea Court. The downside? I'm literally level 23 and only just now experienced my first death in the game because I can't handle the battles of Chelsea Court. It sucks, I'm not sure what I should be doing as I'm so far ahead of the curve. For a heads up, I'm a level 23 Life wizard.
Question, did you do the side quests for wizard city and krokotopia? Finishing them will give you lots of exp, and will level you up so you can beat MB. It takes awhile but you'll learn better spells too. If you have done the side quests maybe try farming a boss for experience or something?
I would also consider doing Wysteria and the first Section in Grizzleheim (actually probably both of these worlds before grinding out random side quests). That way you can explore new areas. Grizzlheim will only have you do 1-2 areas before you hit the cap and need to wait till level 30 to continue. Wysteria is perfect for Wizards that are about your level. They even have a wand that grants an extra pip by completing the quest line. Wysteria is a beautiful world, and very story driven. It will have you running back and forth a little bit so if you just want to battle, battle, battle, then it may seem a little slower to you. I however, rate it as one of my top worlds.
