The size of the abyss in the beginning should only be as big as a small country, but now, with the surge of the abyss demon's population and the efforts of the demon kings as queens...
The abyss should be as big as Ainsley's previous world, but 2/3 of that dimension was just barren places like desert or something.
No one knew how big an abyss demon king or queen's domain could be, but the bigger and more complex the domain was, the stronger the domain would be.
In a battle between non-domain masters and domain masters, most of the domain masters would definitely win without much effort.
However, in a battle between domain masters, since both domains would clash with each other, the stronger domain would definitely be the one winning the battle.
When ability users reach the level of a domain master, if they had more than one ability, usually, only one of their abilities would be the main 'theme' or the core of the domain.