A Power notices this. 

It seems beautiful, in a small way. Watching them, the Power feels a certain restfulness, similar to what they imagine stonefolk might be feeling when they sit on the moss in silence and watch yet smaller creatures wandering about. 

It seems small, and peaceful. But the Power feels like it's awfully lonely for the stonefolk to be the only people in the universe.

The Power reaches out, and sparks life into the air. The stonefolk are round and stout, so as a contrast, they shape the airfolk into sleek, graceful, birdlike features.

They watch excitedly as the airfolk awaken.

And now the treetops flicker with the quick flowing motion of slender silver-bright forms, swimming through the air like shining ribbons.

A few of the stonefolk who happen to be climbing particularly high spot them, and attempt to approach. Most of the airfolk ignore them, though one or two circle round to investigate.

The Power observes with interest.

They consider for a while, and realise that the two peoples may not get along. They create a few planets and cover them with air, then soil, then lush and verdant greenery, and little creatures crawling to and fro. They create portals to each planet. The portals will only let through those who the residents of that new planet welcome. That way, if there is any enmity between the peoples, one or the other of them could escape.

The Power hopes that this is not needed, and everyone can live happily together. Only time will tell.

People notice and investigate the portals.

An intrepid rockperson goes through one of the portals. Their friend tries to follow, and is stopped. The first one tries to go back, and is stopped.

The two of them dance at each other agitatedly.

I can't get through!

The first rockperson taps on the invisible surface. Neither can I!

Are you stuck? Tap tap.

I hope not. I want to come back home. Tap.

I hope so too. Tap.

Thanks. Ta— no, now the first rockperson can pass back through.

...I don't want to keep playing with this right now.

Yeah.

Word spreads that the portals are scary and you might get trapped on the other side.

Oh no oh no, that is not how it was meant to happen!

The Power ponders this problem for a while.

They change the portals: they will let everyone go back to the main planet, and they will allow anyone to pass through to new planets except those who are specifically unwelcome, in the opinion of residents, whether individually or as part of a larger category. The blacklist is shared by all portals on the planet, so that there will never be an unpleasant surprise. They link some of the planets to each other too, by new portals that work the new way.

They make the portals shimmer blue, as if to say, something has changed. Who knows if it'll be interpreted that way though.

The Power checks on the airfolk, too.

It's not possible to find out directly who the residents consider unwelcome – a being's mind is theirs alone – but any expressions of welcome and unwelcome can be automatically noted.

The shimmer makes some people more cautious and others more inclined to investigate, with the net effect that it doesn't take long for someone to discover that the portals are now passable freely.

The airfolk interact with each other uncommonly and cautiously, their wind-stream bodies just barely touching at the edges, sending eddying ripples through each other. They seem more comfortable interacting directly with solid things; some of them have started encoding ephemeral messages in the rustling of leaves.

Of the few that were investigating stonefolk, some have managed to get the stoneperson's attention. One pair seems to have begun trying to figure out a way to communicate, though they haven't yet had much success.