The true light sage gestured for a moment and a denser light gathered around them. It was an odd sensation but it felt like the true light sage had used the golem they were communicating through to create a small bubble of space that was their own. Like a piece of the light elemental planes was brought here in to the world.
This made Walker understand that the level of control over elemental manas would be able to reach an even higher level. One that allowed for him to be able to gather enough in one place that space itself made it a small temporary area. Not necessarily an elemental plane but something above a domain.
The fire dragon or other elemental domains were just parts of the world as it was wreathed in their mana and made perfectly from and for their affinity using their manas. That was just a potent and powerful way for them to stand in the best possible terrain for a battle or whatever they needed.