I am level 23. My wizard has access to Wizard City, Krokotopia, and Grizzleheim. When can she advance to a different world? And what world would be next?
Once you have completed all your required assignments in Wizard City, Merle Ambrose will ask you to investigate Krokotopia.
Once you have been given that quest, you can access the Spiral door by entering Bartleby the World Tree.
After you’ve completed Krokotopia, you can move on to Marleybone, then MooShu, then Dragonspyre. You can visit Grizzleheim at level 5, but cannot return until level 20.
You can preview each of these worlds on the website. Just click See the Game and select "Visit New Worlds".
If you want the prize, you have to build the ladder rung by rung. There are no shortcuts.