Kael Black is reincarnated in an alien body, in an Underworld where low-class demons exist only to serve and die. Without a clan, without protection, and with nothing but his own will, he is thrown into a ruthless system that shapes his power through combat, risk, and sheer effort.

A story of organic, brutal ascension in a crossover world (High School DxD, Shinmai Maou no Testament, Rosario + Vampire, Fate), where power is not granted—it is seized, blow by blow, wound by wound, choice by choice.

I'm responding to Novel_Manga_2624, or anyone else with the same question, and I didn't make the maximum effort to explain.


Chapter – The Source and the Use of Power


All supernatural energy originates from a single Primordial Source. Some call it the Origin, others the Root, Akasha, or the Primordial Sea. The name doesn't matter; what matters is that the Source is neutral and chooses no sides.


What distinguishes demons, angels, humans, monsters, or mages is not the energy itself, but how each one uses it.


Direct, emotional, and explosive energy


Lineage defines stability and power ceiling


Energy flows through spiritual affinity


Fall occurs due to loss of resonance, not physical damage


Use symbols, formulas, and circuits to convert energy


Preparation and calculation define effectiveness


Lineage determines quality and affinity, not brute strength


Energy is innate, controlled by instinct


Presence and spiritual pressure are weapons


Pure lineages increase natural power and may require seals to contain it
