Hephaestus ' reason for creating human killing machines in Horizon Zero Dawn is undisclosed .
Aloy returns to the Banuk Shrine , where CYAN has transferred herself to , and CYAN provides additional information about the Old World but warns that HEPHAESTUS is still active somewhere and seeks to build an army of machines designed specifically to kill humans for some unknown purpose , which is why it tried to seize control of CYAN and its facilities .
Horizon Zero Dawn