In 1977 Diablo arrived on the Earth. After two years of widespread destruction, and a few weeks without any new demons pouring out of the Gate to Hell, a new creature emerged from the Earth. Rumors and accounts swirled for weeks afterwards, but when a picture of the beast was eventually taken and the taker able to survive long enough to get the picture to the public, there was no mistaking that the new creature must be none other than Diablo himself.

However, this wasn't the Satan of Dante's Inferno, or the cartoonish Devil that the Imps resembled. Diablo was a massive humanoid of fire, easily 10 stories tall, with four great horns on his head and a row of spikes protruding from his spine. He also had a short, pointed tail, and large hands and feet with great claws growing from each. The Demons and Greater Demons didn't seem to mind being near him, but his very presence was hostile to all other life. For kilometers around wherever he stepped, everything that could burn burned, and for kilometers more, it was uncomfortably hot. Diablo's mere presence affected the weather, and weather maps showed visible spikes in temperature around wherever Diablo happened to be standing. In fact, Diablo himself could be best characterized as a force of nature. Chuck thought of the adjectives newspapers used to describe him: evil, tall, aloof, merciless, burning, cruel. But above all, they mentioned that he was capricious. To the best of anyone's observation, there was little rhyme or reason in what Diablo did or where in particular he went, and he seemed to revel in the beauty of annihilation. He passed by cities of people that had already surrendered to demons, though as he passed close such cities would still be under extreme risk of fire just as a side effect of his passing. This risk even extended to other denizens of hell. Greater Demons were not harmed by the close proximity to the walking inferno, and Demons were heat-resistant, but Imps would burn almost as easily as humans if they got too close to their flaming master. When he encountered cities that hadn't surrendered, he threw great fireballs at the cities, and it was only if the people in the city surrendered to the lesser demons that he would cease the destruction. However, when he reached Panama he stopped being escorted by demons and began his path of solo destruction, which brokered no chance of surrender or mercy. His path of destruction was relatively slow and meandering, such that it was not until 1979 that he reached Mexico City and destroyed it utterly. People by and large had a chance to flee, and when Diablo destroyed cities they were often entirely abandoned, but his destruction of industry and agriculture meant that even if people weren't killed by Diablo's great fireballs, they faced a future as homeless unemployed refugees at risk of starvation.

In the face of the demonic hordes roaming most of South America, aside from creating a safe haven in the southern tip, the United States was trying its best to take action to protect its own cities and citizens. First, very soon after Diablo first appeared on the Earth, NASA finished preparations to create a permanent colony on the moon. That was more of insurance against the worst, as if Diablo was truly an unstoppable, ultimate evil, the hope was that if worse came to worse, a colony on the moon would be safe from the creatures that roamed the doomed earth. Second, after seeing how ineffective current artillery and heavy tanks were against the Greater Demons in South America that vexed all efforts to contain the onslaught, military researches rushed through with plans to create an IBIS walker. The first ones were taller and more slender than later versions, and less heavily armored. They were about 30 meters tall, piloted by a five man crew, and had two great cannons for hands. They were powered by a nuclear reactor fed by overloaded plutonium, and their humanoid shape made it practical to make them larger than even the largest tanks. However, when the first one was created and sent down to South America for a trial by fire in 1976, the result was disappointing. It engaged a Greater Demon near Manaus, but the IBIS walker was destroyed. A second one was created and stationed in Mississippi, such that when the first of five waves of invasions came, the invasion was utterly crushed. In 1976 a large force of British transport helicopters flew to Florida. Air defenses destroyed some of them, but when the helicopters landed, they didn't unload crack troops, but huge numbers of poorly-armed religious Fanatics. They began attempting to take over the area, but the IBIS walker was nearby. They would never surrender, so the battle that followed was an exercise in futility. South of Montgomery, Alabama, the IBIS walker met huge groups of Fanatics. They had only the crudest makeshift weapons to be used against the huge walker, and some of them rigged up catapults and traps while others tried their best to scrounge military weapons that had some chance of at least damaging the walker. However, captured bazookas were completely ineffective against the walker, as were their traps and catapults, and without any signs of surrender, the crew of the IBIS walker was forced to show no mercy to the mixed force of men and women that made up the group of perhaps 20,000 Fanatics. Its great guns blew them apart by the hundreds and its machine guns, which in the first generation walkers were mounted just below the larger guns, tore into the unarmored paramilitary soldiers, such that it was very quickly out of ammunition. However, its nuclear reactor had plenty of fuel, such that when it was out of ammunition, the walker began stomping the ground and swinging its empty cannons, gruesomely killing Fanatics which ran screaming at the huge walker, hitting it with objects like Don Quixote tilting at windmills, and swarming it and shooting ropes over it to see if their combined weight could bring the walker down where it could be tied up like Gulliver. They did succeed in damaging one of the walker's empty cannons, but the gruesome battle only ended when all of the Fanatics were dead, and the dirty, bloody IBIS walker trudged back to Mississippi to be cleaned and repaired.

That very same IBIS walker was the only serious obstacle between Diablo and the rest of North America. If its battle with the Fanatics was one-sided, its battle was Diablo was even more so. On September 8th, 1980, it had a showdown in Texas, if showdown was the right word for two monstrous creatures engaging each other at distances that, without magnification, made one look like a spec in the distance to the other. An observer on a hill with a high-powered telephoto lens on his video camera recorded the encounter. The IBIS walker shot first, and the shells hit Diablo dead on in the chest. Diablo stumbled, but was otherwise completely unhurt by the powerful blasts. Diablo struck back, throwing great fireballs far into the distance, hitting the IBIS walker. With the first blast, both of its arm cannons melted, making them unusable. However, the IBIS walker was still mobile and the pilots within still alive, so the walker turned around and began moving to the north as fast as it could. It was nowhere near fast enough. Soon a second blast came, which cooked off the artillery shells stored in the IBIS walker, and it blew apart with a great explosion. The observer then stopped filming, and Chuck assumed he got out of the area as fast as he could.

With the slow progress of Diablo through South America and Latin America, there had already been a general migration of people from the southern to the northern states. With the destruction of the IBIS walker it became a headlong panic. Chuck Horner was five years old at the time, and living in Rochester, New York. His father was a radio tower construction manager, and his mother was a teacher. He still vaguely remembered eating dinner with his Dad, and his Dad telling him that the family was moving to Fort Good Hope. His Dad had a job offer up there, and that northern city was booming with population. In addition, in retrospect Chuck was sure his Dad was thinking about Diablo, and how if Diablo made a beeline for Rochester, he could make the city burn by Christmas 1980, and at least Fort Good Hope would be farther than Rochester from where Diablo was currently. So, Chuck's Mom helped him pack up his things and some clothes, telling him that he wouldn't have much use for shorts were they were going, as it only got warm enough to wear sorts about one month a year. She also told him to pack light, and that a lot of his possessions and toys would have to be donated, given away, or discarded. In October Chuck, his Mom, and his Dad all got into his Dad's car, as Mom had sold hers, and had put a pod on top of the car to store extra things. They had sold their house, furniture and all, and did not need a moving truck, and Chuck began the long road trip northwest. He only vaguely remembered when they finally drove into Fort Good Hope, and only later learned that Fort Good Hope was a small town of only a few hundred people in 1945, but in 1980 had a population in the tens of thousands and growing daily.

As for Diablo, he moved through Texas and turned east, and started his path of destruction, moving through Mississippi and Georgia, purposely destroying every manmade structure in his path, while his mere presence was an ecological disaster, killing plants and burning forests wherever he went. With his slow progress, loss of life directly from his solo onslaught was light, but the onslaught was economically devastating. Refugees swelled northern cities, and food became scarce, but with most of the Midwest spared the food shortages weren't too bad yet.

After years of torment, by the early 1980s all of America south of the Mason Dixon line but east of Texas was completely destroyed, with barely a single man-made structure still standing. Washington D.C. was destroyed, and government moved to northeast Siberia. Diablo, in his capriciousness, had not gone west of Texas since then. The middle south states were home to nuclear plants, which powered half of the country as high-power wires had previously crisscrossed the United States, bringing cheap nuclear power to all. With Diablo's destruction those plants were operating at much diminished generation due to the lower demand, but so far had been left alone. Diablo turned towards the nuclear plants, and finally began attacking them, as well as the new cities and towns that had spring up close to them. Most were shut down and their control rods lowered before Diablo turned on them, and most were destroyed relatively cleanly, with radiation limited to within a kilometer from them. However, when Diablo attacked the Denver nuclear plant, he destroyed the control room first, and his fireballs happened to lock the control rods in their retracted positions. Previous plants used 4% enriched uranium, but new ones used 14% enriched uranium for increased efficiency, which also made them more dangerous and increased the speed of the reaction. Thankfully, it was still physically impossible for them to make an uncontrolled chain reaction like weapons-grade uranium, and when the reactor exploded it was an explosion of a distinctly conventional sort. But the fallout was terrible. The area was fully evacuated, but a huge swath of Colorado would be hostile to human habitation for decades. Further, more than anything else the move through the Midwest caused widespread famine all around North America, and a lot of people starved to death in the months and years following. Concurrent with the destruction of the Midwest was a second invasion, this time a group of British Fanatics that came on cargo plans and quickly look over Nain in Labrador and began moving to take more cities. However, this second invasion was even more ill-prepared than the first, and in addition to an IBIS walker in the area, there were plenty of regular soldiers as well. They were still using M16 assault rifles generally, but now were armored with almost full-body Kevlar body armor with ceramic plate chest pieces. In addition, the IBIS walker was a second-generation machine, which had been improved in three ways. First, it had a more powerful power plant, allowing it to not only move faster, but for it to be practical for more armor to be applied to it. Second, it was much shorter, and was about 10 meters tall instead of 30, but much bulkier. Second, it was no longer manned. In a remote, secure location operators would remotely command the IBIS walker. This was the beginning of the integrated circuit era though, so it was only minimally independent. Even so, the automation allowed by the onboard computer allowed faster targeting and more accurate fire in addition to freeing up room previously needed for the crew, such that second invasion was crushed swiftly. A second wave of cargo planes tried to land, but Mexican jets destroyed most of them, and only a few Prophets landed. They engaged the robotic IBIS walker, but while they had been so effective against tanks at Khantayskoye Lake, the large IBIS walker had safeguards in place so as not to be as easily stopped by electricity. The combined electricity of the few Prophets was not enough to overload the robot, and the IBIS walker easily killed the Prophets. Diablo continued his meandering path of destruction through the Midwest, aloof to human politics. When he destroyed the main space center at Winnipeg the moon base was stranded for a few years, but it was already mostly self-sufficient by that time, and a few years later a small launch facility in Siberia started sending and receiving rockets. After Diablo had finished destroying every manmade structure east of the Rocky Mountains, Los Angeles was spared for the time being as he began moving toward New England.