From House of Hozz
After discovering their new door into TwinWorld, the hozz brothers naturally want to explore. The following stories may interweave and overlap.
Naturally the hozz brothers explore The House first.
Next, they should venture outside, trying to make sense of their surroundings. Perhaps they will meet the Fayrie and find some of Durand's old friends. Perhaps they will have a brawl with some of the Zarth.
A few ideas
It would be great if a few of the hozz brothers get out above ground and meet the fay, while a few get out below ground and meet the Zarth. Then, when they all get back together and try to explain what happened, they will have wildly different stories.
What should the first story be? Should it be a story of rescue? Can we fold in the form of some of the old fairy stories here? It might be neat to open with a more formalized story. Something that conveys the iconic nature of TwinWorld. Ziggy
Oswald (and others?) discover the library, read (or try to, can they read runes?) some books, perhaps discover some pertinant plot points or backstory.
If the House of Hozz is actually in the middle of the Garden of life, then anyone should have to escape past giant carniverous plants to get anywhere else. This, in itself, would make a good series of stories. Using rope and grappeling hook to bridge deep gulfs between the plants. Fighting off vines. Trying to evade a Sphalin, only to find that it is attacking the plant they are climbing instead of them. Finally breaking out into the wider world to behold another (perhaps even more alien) landscape.
Fire Bird attack
Any of the brothers who set out above ground may become separated during an attack by a fire bird from the Outer Fire. They are shielded by Fay enchantments, and get to meet some of the inhabitants of the forest.
Tumble into Turmoil
A dramatic way to introduce Turmoil is to have one of the brothers stumble into it. A branch of Turmoil made of fine sand and pebbles would act like lightning sand, and suck anyone down almost immediately. In the frigid depths, pummeled by rocks and choking dust... um actually you would probably die. Do we want to kill off a character early? Otherwise they would (somehow) come into a stable section (maybe from the roots of the garden of life?) or discover a worn out piece of Zarth machinery (these things should be all over the place) in which to take shelter. From there... work back to the surface, go deeper down, or wait until rescued!
If the brothers gain powers in TwinWorld, they should each have a situation in which they discover them. These should probably be worked into the other stories, instead of inventing a story for each revelation (which seems a bit cheesy).