What's the one thing worse than Hell on Earth? When The Legions of Hell decide to invade that most holy of places, Heaven itself! In works that focus on the conflict between Heaven & Hell (which to be fair, includes most works where Heaven and Hell appear as opposing sides) this will be the ultimate goal of Hell, and is usually kept from happening by an Enemy Civil War or other big conflict among the demons, with the major threat being some ambitious demon or other villain seeking to unify them. Oftentimes, invasion of Heaven is an Evil Plan that the heroes need to stop before it comes to pass, similar to Hell on Earth. But for those times when things truly go From Bad to Worse, the demons will launch an all-out onslaught against Heaven, seeking to corrupt or destroy the Council of Angels, the Fantasy Pantheon, or even the Big Guy himself, with the heroes having the unenviable task of stopping everything from being destroyed. Since situations like these are nearly always Grand Finale situations, they are usually big spoilers. Compare Hell on Earth and Rage Against the Heavens.
- This is Hell's grand plan in the Spawn series, with Hellspawn in charge of gathering souls for Hell's army.
- Wendy Alec's The Chronicles of Brothers series, a series of Christian polemic novels about the in-fighting between the brethren Gabriel, Michael, Christos and the black sheep of the family, Lucifer. The aforementioned Lucifer tries this on more than one occasion, only to be humiliatingly bitch-slapped by his brother Christos and the lads. As Mrs. Alec's novels follow pretty much exactly the Christian perspective and what is "known" (in the Bible and related sources) about the nature of Heaven and Hell and their denizens, you wonder why Lucifer even bothered... it's in the Bible, you'll never win....
- John Milton's Paradise Lost is the trope codifier/forerunner by depicting Satan's rebellion against God.
- The above novel inspired a subverted example of this trope, the His Dark Materials series, where The Legions of Hell are actually the good guys.
- In Dungeons & Dragons, if the Blood War between the demons and the devils ever ends, the Upper Planes can look forward to a full-scale war with the fiends as they launch an invasion.
- In the finale of Diablo III, Diablo, upon his rebirth as the Prime Evil, launches a full-scale assault with all his demonic forces on the High Heavens, seeking to destroy the Crystal Arch and plunge both the Heavens and Sanctuary into darkness forever. Because Diablo has become the embodiment of all seven of the Great Evils in one being, the angels do not have a chance in Heaven or Hell of stopping him, meaning that you, as the Nephalem, have the task of stopping Diablo and destroying him once and for all.
- In Titan Quest: The Immortal Throne, when you reach the Elysium you find out that the heroes there are fighting back the hordes of shades and demons serving Hades, which has gone mad with power. Odder than the standard example because Elysium is still part of Hades's kingdom.
- In Super Paper Mario, an army of Skellobits from the Underwhere invades the Overthere, where an army of Nimbis rises to fight it.
- This is basically what happens in the True Demon Ending of Shin Megami Tensei III: Nocturne.
- This is what the last few levels of Disgaea are based around. You're the one controlling The Legions of Hell. It turns out to have been a part of a plan cooked up between the guy in charge of heaven and Laharl's father to make sure he ends up as a Noble Demon and not a Complete Monster.
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