Maybe you don't have access to Bartleby yet, check with Headmaster Ambrose if he says you can go to the Oasis yet. If not, finish all the quests in Wizard City first.
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, then Celestia. 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.
