Rebirth of Evil Ancient Being

In the Chaos Era, a lot of legendary beings and races are born to compete for hegemony. It was the most brutal era causing a lot of races and beings to die. But there was a single being who managed to fight against many enemies be it races or legendary beings. He was known by many as an elusive, unfathomable entity at that time and gradually earned the title—Nightmare. Because it was he who successfully won the hegemony and killed almost 90% of living beings at that time and the rest survived oppressing them with fear and terror. His name became the legendary taboo as time passes until he died due to severe injuries. But that still did not make the survivors cheered but instead made his name became eternal. A million years passed by, the survivors gradually reproduced and hid in the dark while letting their offsprings control the world. ......... On the lowest level planet in the Universe called Earth. A demon tribe leader found a strange violet gem that was hidden by the previous tribe leader with 'Nightmare' carved in it. Strangely, he managed to receive instructions from the gem to sacrifice 100,000 living beings in exchange for one wish. It took the demon tribe leader hundreds of years to successfully kidnapped weak or ordinary people and successfully resurrected a being which seems to be far from what he thought. "Is this a blessing to my tribe or a curse?" He said to himself. He didn't know the answer but if the survivor of the Chaos Era knew it, he will find out what kind of entity he has just resurrected!