Inspired by the above^

There is a certain physical property of these coastal biomes, that forms glowing portals on top of the water at night once a month (it is an unpredictable and magical occurrence!)

Planets that form with a certain chemical composition (different from earth) are prone to this happening. Maybe they have extra phosphorous or nitrogen or something

The physical property is a type of bioluminescent bacteria, “the emerald baceria”, that is bound to evolve in such climates. And this bacteria bonds together and taps into the sub-molecular fields that compose the universe, to draw on the energy of the bacteria in the other planets.

The coastal biomes have evolved around this. The trees, fish, plants, birds, coral, turtles, throughout time have passed through the portals, so the planets are similar in climate and ecosystem, and connected together. This bacteria isn’t only in the ocean, it’s in the rivers, mountain, drinking water, and the life forms that consume it are also connected to the other planets.

This creates a sort of collective subconscious. (There needs to be a cool distinct twist here, to not go too far into Avatar blue people territory)

The culture of humanoids that live in these biomes also has a culture of going through the portals. The thing is, when you go through a portal, you can’t control and don’t know where you’re going. And if you are not physically touching someone, you will go to different places when you walk through. Maybe you get teleported somewhere where you “need to be” (perhaps to learn lessons).

Sometimes, it doesnt work, and you walk straight through to the other side, because it’s not meant to be.

If you want to go with someone, you have to hold their hand. And it can work even with 5 people all holding hands! But nomatter where you go, it’s always a similar biome.

The culture of humanoids has evolved around this. They are travelers, who make temporary friendships as they stay different spells on different regions of the inter-planetary ecosystem. They value living with their whole heart and mind, but know that everything is temporary.

This sets the scene for different types of levels, adventures, challenges, and friendships for the game!