when he saw the girl and the lab scientist he first manipulated the scientist to release the girl he could feel the energy in her was different it was like it was mixed in her skin and body like those who are turned into demons.
there are three ways people can turn into demons one by absorbing the blood of any dead demon without asking them since they are dead the blood of dead belongs to the one who finds it.
two by making contract with a demon which will give you his blood in return for anything for what a demon wants it will depend on the demon sometimes they ask for your life energy or serving them for few years it could be anything and sometimes they give it for free just for becoming strong because if someone which used the blood of a demon by contract or for free when the person die their cultivation and the blood given to them will also go back to the demon so the contracted people who become demon through contract are called demon kin and if a demon kin gets children after contract their child which get the demon bloodline will also be bound by the rule that when they die their blood and cultivation will go to the original demon who gives his blood making his bloodline stronger by every new generation created by demon kin stronger but if the main demon dies the contracted demon kin becomes free from contract.
three when a person has hate or grudge against someone and they are not strong enough to defeat them they can always make a pledge to the heavens and gods to acknowledge their hatred and ask for strength in the name of heaven but it's up to heavens and gods to acknowledge their pledge if they agree the person gets the strength but their is always some demon gods who notice these negative feelings first and gives the said person blood as power and the girl with the white hair is also one of unlucky ones who was chosen by a demon god.
she did get power enough to kill even immortals but her fragile body was unable to hold such power and it was exchanged with life force to make her body strong enough to hold the power the girl mostly have a few months to live at most a year so he decided to save the girl and make her his loyal pe-subordinate.
he used his power to free her her face was really beautiful her eyes were hollow like she is a dead person he could see in her that she doesn't want to live he thought.
'it must've been tough on her well I'll ask her later'
he then made every one in the lab his minion and took the data required to get to the bottom of this organisation and control it he also asked all information the scientists have he was able to locate a few more bases just like this in the whole city.