If they have a lot of Chaos spark then they can refine it into Chaos essence in a safe and contained manner. With enough Chaos essence, he will be able to create an Apocalypse Weapon or even steal a Cosmic Source from the void universe.
That last one is a dream that can't be realized in the near future. But presently, to destroy all the living things in his world will not only set him back in time and resources he took to create them.
It will also reduce the time it takes for him to acquire chaos essence. The death of every living thing will also affect Hadrikomania by weakening her, which will in turn weaken him.
He made up his mind and said to Hadrikomania, "Fine. We will take things easy. There's no rush anyway. Legion isn't ready to make a move against the first sage yet."
