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.
What are the missions to complete to get to Krokotopia?
You will need to finish Unicorn Way, then get to the other three streets, which can be done in any order (Fire Cat, Triton and Cyclopes). You will know you have finished the streets because you will defeat the major boss and then get sent to Merle.
Merle will then send you to find and fight two death bosses....the last is very tough.
Once you finish the second death boss, you will get sent 'under the waterfall' to find the death school. Once this quest is done, it is on to Krok.