Hell world is not only sick desire to reset world, it was ust outcome from inside invasion by literal alines. Using time of uneven battles, outside forces tried to steal minerals for own use. Key word is "tried". As greedy dragons are, Basilisk personally ended thier existance on than Earth.
Few ran away and adapted, copulated with demons and humans alike. Hybrids of aliens got accepted after death of oryginal gene givers under strict rule of no digging for informations since thier dairies are kept in personal librery of His Majesty.
City of hybrids also got demon as head of council to prevent revolutions, according to residents having more than three powers at once, and being able to control all of them at same time. Highly dangerous individuals with high loyalty towards New Order Creator got into army as secret service and trained assassins. Most of special forces can pose for killed people to not raise suspiciouns until body started rotting badly in not so active offices.
Underground people... That's one tough to take in. In century of escaping, some aliens decided to take underground for thier home, abducting people, forcefully keeping them until giving birth, keeping child in for experiments to see if blinding another generation takes faster effects. Few times one demon female dragged about to be rape doer dead, official forces took courpse for secret invastigation, the female demon turned out to be head sientist. Results came back as expected, completly not human dna, not even 1%.
Foghart actualy wanted to encounter at least one alive one, to try and communicate. Looking into random hole he screamed in demonic dialect "You better not abduct me, I will kill you!" and of course there was a webbed hand with long claws reaching for poor victim. Mer-demon was faster. Tearing away unprepared predator from underground at soulless night "Here you are, trying to kill me." creature sniffed air grugling like having internal bleeding constantly, to screaching of even for demons unholy sound. He slapped creature with stashed sword, keeping bit of blade to throat "No going to tell me anything, are you?" pale creature tried to protect itself from blade with free hand. Armor Foghart wore today is made from Basilisk's scales, with special enchantment. Creature started to pft out air, more came crawling out of opening. Mer-demon eqipped helmet, slashing held creature'd head off. Nearaby demons seen thier kin in danger, jumping under his command "Use your trusty blades to cut thier throats, sides of torso and any point of spines. No mercy. Order carried out of Lair."