The Abyss: A bottomless pitt filled with dimensions in the shape of a spiral. As someone travels further down it gets more dangerous.

The Outer Planes: Dimensions outside of the abyss. For example the energy plane someone can access it threw techniques or threw inborn talent to access and use certain energies.

Corruption: A disease that extends the life and gives powers to those immune to it or otherwise turns them into an undead or monster.

The story takes place on Earth but other dimensions and energies have corrupted it and have expanded it and changed it. Society has changed into a strength based feudal system. With humans being the weakest and struggling to survive in the new world.