Planar Travelers

Braythe is a reality of its own, a unique dimension connected to a variety of other alternate realities. It can connect to any cosmology via natural conduits and artificial portals, but it doesn't have a set of different planes like most other cosmologies.
This means that planar travelers who find their way to Braythe always come from an alternate reality. And while journeys to other planes may be common in some worlds, entering a completely different cosmology is usually a pretty rare event. This means that most planar travelers have never heard about Braythe, and usually end up here on accident, or following someone returning to Braythe.
Such visitors might come through a natural conduit (which doesn't have to be placed in a comfortable landing place), or step through a portal. One of the best known doorways to other planes in the world of Ashandri is the portal to the plane of fire in the Ember Wastelands, but there are a number of others - some magically created, some occuring naturally.
Planar Travelers arriving in one of the worlds of Braythe often believe they ended up on a regular world of mortals, just with a somewhat unusual violet sky. Once they find out the truth, they are often awed (or terrified) when they realize they ended up in a different reality. Some of them get curious and decide to stay, driven by a desire to explore this whole new universe. Others actively seek out gates to other dimensions, using Braythe as a travel hub to alternate realities - regularly returning, but only to get to their next destination. And a few ones are stranded in Braythe, desperate to find a way back to their original reality - sometimes not even knowing for sure how to identify it.
Of course, planar travel works both ways, and some residents of Braythe have made friends in other planes. Those friends might come along when the person returns home, and sometimes, they decide to stay.
With such a vast variety of different planes accessible from Braythe, not all visitors are humanoid (or even mortal). Sometimes, supernatural entities see Braythe as a whole new opportunity, and visit the dimension regularly, or even set up a new home in one of its many worlds. Especially worlds like Ashandri, with its history of making deals with powerful beings, attract many such creatures.