The Demon Dogs
If you have seen a Demon Dog, it means you are too late. For you, that is.
The earliest days of the Great Catastrophe caused madness in domesticated animals. Dogs were the hardest hit. Still unknown to this day, dogs turned on their best friends and became bloodthirsty. Some feel the Rabies virus mutated and all vaccination efforts failed. Others described a radiation sickness that melted the canine brain centers, dogs would go feral and become violent before dying. After the initial waves of disasters, the pets who survived bred with wolves and other alien creatures. The offspring became the topic of horror for years to come. The flesh-eating canines stalked the injured or unwary travelers. If a child was left unattended, it would not be unheard of that a demon dog would snatch them away. Parents who keep their children safe by telling them of the dark days when the demon dogs would hunt the abandoned homes searching for survivors and unruly sons and daughters who ran away from home.
Legends even as far back as 2017 speak of a haunting of cemeteries by Demon Dogs. From an ancient file newsreel: The report is hard to verify at this time. It is the best information on how Demon Dogs could have arrived here. The estimated change in behavior was about 2136
Reports from residual social media are sketchy and although most have since disappeared, stories from village elders or parents keep the notion alive in the hearts of the young.
Variations & Mutation
Another possibility was an actual interbreeding or mutant deviancy in the canine species. This theory has been bolstered by a video file from a smart home device shortly after the disaster.
Ancient cultures as far back as the days of Vikings often refer to a demon dog as a Hell Hounds. They often describe the creature as a black dog with red eyes, malevolent and usually a bad omen pointing to the impending death of the one witnessing such a creature. Hell hounds are said to be repelled by a number of cleansing agents, including holy water, gofer dust, and devils shoestring. Plenty of other cultures have names for the menacing beasts but for all intents, these myths have no evidence of reality.