All in good time, young Wizard. If you're just getting out of Marleybone, you're not prepared for what you will face in Dragonspyre.
Just as you had to complete all the required quests in one world to progress into the next, you must complete your required tasks in Marleybone before you will be invited to hold they key to MooShu.
If you are at the beginning of Mooshu, then you have a long way to go. Just like the Professor said, you aren't prepared for Dragonspyre. But just for good measure, you have to defeat the Oni no-death in the spirit world and then defeat the Jade Oni in Jade Palace.
