He pokes at his own power again and goes intangible, "Does it stop me like this?" He wonders, trying to move his hand through one of the hexagons. 

At first the hand doesn't go through, and then it does. "I think I can let you through if I want to."

"Huh! More twin stuff, or can you let Henry go through without dropping the shield, too?"

The alts try... "It might be easier to do with Tobir?"

"...That doesn't feel quite right." He has since acquired a collection of blue shapes hanging in the air. "It feels... more correct that's only him."

"Huh. Can you," still intangible, he offers his hand to Heri, focusing for a second, "Can you touch me?"

Tentative poke?

Success! "And if this is going the way we think it will, Henry won't be able to," he pokes Henry's shoulder, focusing on letting him touch him, but his hand goes right through.

"So there's twin exceptions. And we can heal each other? I wonder if there's anything else, or if that's it?" 

"Not sure how to figure out, besides being vigilant about it."

"Maybe we will find a better power analyzer at some point. For now, I think we have quite a lot to work with. Tobir, do you think you can go intangible by accident? When you're startled? Does either state feels harder to maintain?"

"Hmm... I don't think this is any more tiring than being solid?" Tobir switches back and forth a couple times, making sure to check that he's not clipping into anything when he turns solid, "Switching's maybe a little tiring," he decides, "But once I'm in one state it's fine. I'm not sure about doing it on accident," he adds, "I might have to get used to it more to make it happen when I'm surprised. Switching takes a bit of focus."

He turns to Heri. "Similar set of questions, changed as applicable. Can you do your force field accidentally? Is it tiring to maintain?"

"Pretty much same answers as Tobir? Not sure if it can happen accidentally. And keeping these up is not effortful." He waves at his collection of glowing regular geometric shapes. To Tobir. "Does it feel like anything when you're intersecting something solid? Actually... do you think you're intersecting air when you go ghost?"

"...I have no idea. It feels like I'm still breathing something, but..." He pauses for a moment, trying to stop breathing. After a moment of this, he shakes his head and starts breathing again, "I need to breathe, yeah. Maybe I'm just intangible to solid stuff? It just feels like I'm moving through air when I go through something solid."

"We can do some tests with water and gases. It could be dangerous for you to put your lungs underwater or through harmful atmosphere. We can test that with some gas that would have a noticeable effect."

"Sounds like a good idea," he agrees. "We should figure that out in a controlled environment before it happens somewhere else."

They nod. "A lot of things to test. Hey, do you think you can turn other people ghost? And you're turning your clothes, how much cargo can you take?"

"Could he turn one of your forcefields intangible? Or move them to inside a rock or something?"

"I don't think my forcefields can be move..." He thinks of something and makes a cube that starts smalls and grows. "except by growing, apparently."

"Good question," Tobir agrees, "I have no idea how much cargo I can take. I'm taking my clothes and the stuff in my pockets right now, but... I feel like I probably can't take a whole person? But we can still try. Stands to reason if I can do it at all I could do it to you, right?" He asks Heri, holding out a hand.

Heri takes it.

No such luck. "Guess not," Tobir says.

"Okay, so, things to test: cargo capacity, whether I can ghost through gasses and liquids, whether I can ghost Heri's forcefields, and how strong are your forcefields, anyway, what can they block... oh yeah, how does crystal magic interact with this stuff, like, do the anti-magic crystals do anything to our powers? And..." He thinks back, trying to find what it is he's forgetting, "Right! Checking to see if the powers did anything else to our bodies besides heal Heri's sore throat." He looks around to see what the others have to add to the list. 

Check (carefully), the limits of their healing powers (which will likely involve just wait and see when they get hurt/sick). Besides the anti-magic crystals, see how the crystal magic in general interacts with their powers (Could Tobir interact with a crystal while phased out? Can Heri's shields be assimilated by crystal?). General stress-testing of their abilities, how long can they maintain them, and see other possible limits, how far Heri can make a force-field? How large? And so on.

The necessary tests having been lain out, they begin to experiment!

Testing reveals that Tobir can ghost anything which is totally contained within six inches of his skin, that he can, in fact, ghost through liquids and gasses (they still haven't figured out what it is he's breathing, though), and that he cannot ghost Heri's forcefields. If he throws something he'd ghosted with himself far enough that the whole object is more than six inches away from his skin, it becomes tangible again.

When he's ghosted, he can't interact with anything non-ghosted except for Heri and the surface he's standing or lying on (there's some wiggle-room here, he can sometimes trick himself into thinking he's lying on something by sitting down, for example), and this includes through crystal-use. He can't use crystal magic on anything besides himself and the things he ghosted with him. 

Heri's forcefields can't be move once they stop growing, and he has to decide the final shape before manifesting them. He can't force two shields to intersect. Shields can handle quite a lot of force and pressure, but once they are broken, they pop like soap bubble. Relatedly, the anti-magic crystals will destroy them pretty easily. Crystals can't assimilate the forcefields.

Shields need to start somewhere a few feet from Heri, but can otherwise propagate and cover a large area.

They test how large. And then again. And again.

Soon, their entire island is covered under a force-field dome.