I was searching around for other entities in the solar system, and a couple of things popped up...

The inner core is tremendously hot, and in terms of inverse temperature, would be quite cool. This would be the physical area where the effect of the "inner plane entities" would be present, they are distributed in space, but they are restricted to the "time" of the white dwarf core. And the only way to take a journey there would be if the 4th density body has been formed, which is something many of the Elders had accomplished, which is why Olaf found Sanskrit speaking giants on his journey.

Another thing to consider is the fact that the Earth and the Moon share cores (reminds me a lot of Harry Potter and Voldemort's wands!) so while the core is spatially separate, inhabitants of Fowser and the Earth's core might be the SAME.