You still need to earn access to those areas by completing your current assignments.
Colossus Boulevard is a much more difficult area, and Merle must ensure that you are ready. He will give you access to Colossus Boulevard when you have completed all your other assignments in Wizard City.
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.
If you want the prize, you have to build the ladder rung by rung. There are no shortcuts.
