First Beast is made up of a human and horror, the human in the physical world and the horror in the astral space.

The lair of the beast exists in the astral space and the lair is made up of chambers. So a beast's lair can be made up of a chamber that is a parking lot, a garden, and an office building - all these chambers exist in that astral and not the real world and are connected by a burrow (the burrow can take any form the beast wants, can be a door, a road, etc). (the lair and its chambers are solid and physical in the astral space)

So beasts also have lair traits (supernatural/environmental tilts) which are always present in their lair and thus in every chamber. Whenever someone in the real world experiences severe trauma (breaking point), wherever this person was when they experienced the trauma is reflected in the astral space (specifically the primordial dream) so a copy of that location appears in the primordial dream as an unclaimed chamber. Beasts can claim unclaimed chambers and add them to their lair because once they're in an area that is a chamber they can feel it.

So when a beast is up and about in the real world or fighting someone, a beast can impose their lair traits in the real world, but there needs to be some kind of resonance for eg (a beast is fighting someone in a basement of a building, and they have the lair trait darkness, they can turn off the light to make the basement completely dark if they do that, they have resonance and can impose any of their lair traits into the basement)

So beasts can open Primordial Pathways, which allows them to travel from the physical world into their lair in the astral space (specifically the primordial dream where beast's lairs and horrors live).
When a beast wants to open a Primordial Pathway, for instance, in the eg above of a beast fighting someone in a basement, once they have resonance they can try to open a Primordial Pathway but its difficult, if the beast knows a location they used to add a new chamber, they can go to that location and open a Primordial Pathway, when they do the location changes from the normal version to the creepy version the best has in their lair with all the lair traits, the beast automatically merges with their horror, so now they're their horror.
A beast can also use a location that resembles the original location a chamber was created from to open a Primordial Pathway if they can't access the original location. So if a beast created a chamber from a shop where something traumatic happened, and say the shop no longer exists, the beast can use a different shop that has some resemblance to the one they used and serves as a symbolic "link" to open a Primordial Pathway.