In this world, demons don't invade the world of humans. Instead, humans invade the world of demons. The leaders of the invasion are Jesus Christ and Buddha, who both had their memories of past lives one day restored to them.

The year is 2015. The Common Era Calendar is widely used all over the world, as it has been since the decline of most religions a few centuries ago. Suddenly, in Rome and Bangkok, Pope Francis and the Dalai Lama clamp their hands over their ears and doubled over in pain. They see each other in their vision and shirk in fear. They remember who they were before they were re-incarnated in their current forms. Jesus Christ and Buddha have remembered their past lives, and remember the time they worked together to screw over hell.<br><br>Two years later, the world is in chaos. The Dalai Lama, under Buddha's control, manipulated India into manipulating Pakistan into starting a nuclear war with China and its allies. Pope Francis, acting under Jesus' directions, manipulated the US into fighting a brutal war on two fronts. The world is in chaos, and the superpowers of the world have collapsed outright or are on the brink of collapse.<br><br>Jesus and Buddha used this to raise massive armies for their crusades, and have funded them with all of the wealth of the Catholic Church and the monasteries of India. It was a massive endeavor that spanned dozens of nations and incorporated billions of people. And it was entirely for the purpose of starting a holy war against hell itself.<br><br>Finally, on January 1, 2023, the largest army in human history was at the shores of the Red Sea. The morning of the attack dawned, the soldiers stood ready, and the advanced naval craft of the crusader alliance blasted their way through the waters of the Red Sea. They made landfall on the Mediterranean coast of modern day Syria, and began their push towards modern day Israel.<br><br>Heavenly host and demonic legion clashed on the mountains of the holy land, as the first battles of the Heaven-Hell War raged. The first battles of the war ranged from Samaria to modern day Turkey, and the outcome hung in the balance as the sun set on the first day of the year 2023.<br><br>As the days turned into weeks, more soldiers flooded in from Africa, Europe, and Asia. More angels and archangels flew in from heaven to clash with the hordes of demons, fallen angels, and devils from hell. By the end of the month, the length of the front was so long it stretched across the whole of the northern Middle East. The war was still at a stalemate at the beginning of February, but the humans were getting close to Jerusalem, and were already clearing out the important holy sites.<br><br>The war caught the attention of other pantheons than just the Christian one. The gods of the Hindu pantheon were on the sidelines as their most important members were possessed, but other gods had taken sides. Surtr marched an army of fire giants out of Muspelheim to wage war against heaven. Zeus himself rode lightning bolts into battle on the crusaders' right flank, and not a single demon remained on the Greco-Turkish border by the end of the month. An and Enlil turned Babylon into a fortress city that blocked the Euphrates River and served as a crucial bulwark against demonic counterattacks. Chemosh, Moloch, Dagon, and Hadad marched their own soldiers out of modern day Jordan to clash with the fire giants. Horus himself disappeared into the desert to fight against Set, who marched an army of daemons into Egypt from Libya.<br><br>As February turned into March, the war was spreading across the whole of Western Asia. The outcome of the war still hung in the balance, but it was obvious that the loser would have trouble surviving. If heaven lost, hell would conquer earth. If hell lost, heaven would conquer hell.<br><br>The war raged on for five years, and only ended because both sides had to band together to combat a massive threat. Heaven and hell had been so weakened by the war that they had to come to a peace treaty to defend both realms, and the realms of the living and the dead, against a threat from outside. That threat was of a being so powerful that its very presence caused both realms to shudder.<br><br>Hell and heaven are at peace once more, but the invasion is still fresh in everyone's minds. How will the inhabitants of hell recover from the five year war? What has the world become in the absence of the superpowers? How has the world adjusted to the loss of the Gods of the Hindu pantheon? How has the presence of gods affected the world? What being threatened heaven and hell, and what happened to it?<br><br>Take your pick, because I don't have the time to answer every one of these questions.