Clearly the Old One had the capacity to kill - or easily deliver some sort of final ending that sounded remarkably like death.
In Garth Nix's Mister Monday, it's suggested that the Old One possesses the power to cause death or deliver a fatal outcome. The quote highlights his formidable nature and potential threat to others, emphasizing his dangerous capabilities.
The statement underscores the Old One's threatening presence, illustrating that he has the ability to end lives or dramatically alter situations with ease. This reinforces the danger he represents within the story's context, positioning him as a significant and formidable force.