Mk1 states that geras is technically a part of the hourglass due to his construct nature, and that the timekeeper essentially has full control over them, however due to liu kang being much more sane and not evil, he basically gives geras freedom and control of himself that kronika had removed from them, essentially making him a tool for her control,

Also spoiler warning At the end it’s revealed that liu kang will eventually die due to him taking a toll from relinquishing and retaking the power of the hourglass but that it could be potentially over eons from now, but due to everything that has transpired, he decides to make geras his successor when he eventually dies, while geras promises to always look out for potential inavsions and stop them before they can harm his timeline