WMG: Light and Dark The Adventures of Dark Yagami
Everyone will be brought back to life
By someone writing "everyone" in a "Royal Life Note." However, because the writer did not specifically write "everyone who died in the battle," this will bring everyone who has ever died back to life, causing overpopulation to the point of mountains of people crushing one another. The conundrum will force L and company to team up with the Yagamis and start Death Noting people for the sake of sustainability.
God was afraid of L because he delegated all death-related powers to the shinigami
Unless there is a pantheon sort of setup involved, why have an all-powerful God in addition to element-specific deities? The reason is that in the Light and Dark-'verse, God acts more as a theological "president," not having absolute power over all facets of life. This being so, he would not have been able to stop his own death if L caused it.
Mikami was not life-noted back
Light, being the clever bastard he is, believed that Mikami would be useful in the future, so in the Death Note he wrote the circumstances of his death as "Teru Mikami dies before revealing the full name of Kira, but miraculously comes back to life before his autopsy is performed and makes his escape, then dies at some indeterminate point in the future." Light turned out to be right about his usefulness, though Mikami presumably died soon after sniping the random slimy dude from the police helicopter.
Near, Mello and Matt all make reappearances because there are more than one of them
No One Steve Rule
in this fanfic; instead, we have two Nears, two Mellos, and two Matts: the first set are the Wammy kids we know and love (Mello dies, comes back after making a deal with Blud, dies again and stays a ghost until possibly being life-noted back in chapter 32, Matt dies and just stays dead, and the elder Near first appears in chapter 18 or possibly chapter 6, and stays alive until being fed poison toast and apparently put into a box full of poison moths in chapter 39). The second set are the children of Wedy and Lind L. Taylor from D'ark's spinoff "The God of Time With No Name ~ Light's Real Name REVEALED!"
which makes their deaths at a younger age all the more disturbing.
The second Matt is kidnapped by "creepy dude" who mistook him for Mail Jeevas (due to him possibly also being in a car accident around the same time as the "real" Matt) and sacrificed him to a volcano god on false pretenses. The second Mello is either mistaken for Mihael Keehl and brought in to help L's forces in the final fight, or may not have even made an appearance, since the true Mello may indeed have been life-noted in chap 32.
The second Near is the one who first makes major appearances in the fanfic, is actually named Near (as is shown by the "protagonists" being able to write "Near" in the anti-life note and kill him whereas they cannot do so for L), and is tellingly less mature though just as hapless than the canon Near; he is mistaken for the real Nate River by Dark (the dead Near is called a "new" agent in chapter 7, which implies this Near is not the same Near who helped L capture Dark in chapter 6) who tries to assassinate and eventually sacrifices him before he is brought back to life (somehow, despite being anti-life-noted) along with "everyone" else in chapter 32.
According to the author on his Twitter account, this Near may have been later death-noted by 1000 shinigami at once when he inadvertently flew his Lego rocketship into their shinigami ship. Or possibly the "canon" Near suffered this fate whilst the younger Near was still anti-life-noted, and it is the "canon" Near who was brought back in 32, despite retaining the greater childish qualities.
The similar names may be explained by Wedy subconsciously naming her children after students who her husband (Lind L. Taylor being L Lawliet's predecessor in the Light and Dark 'verse) met.
Light is half the main casts' daddy
In chapter 38, Dark dies in the earth-destroying nuke
, and Light survives. Almost immediately afterward, Dark possesses Light's body. For the rest of the fic, Dark is possessing Light's body and has Light's DNA—as much was even said when they used Light's possessed body to clone Might Yagami. This means that—if Dark sexed with Samanther between chapter 38 and the ending—LIGHT is actually the father of Dark, Light, and Night. Not only that, but the epilogue stated that Light and Samanther are the parents of L, which means that L, Dark, Light, and Night are all direct siblings (even thought Night's supposed to be a clone...).
Ryuk wrote this fanfic.
Because he wanted a laugh.
By Reset Note-ing
the Khaos Konflikt, Dark indirectly destroyed the universe.
In chapter 33, one of the chapters removed from history due to Dark finding a Reset Note and killing Khaos early, Mello uses a time machine to go to the future (and then the FUTURE FUTURE due to the future not being quite futurey enough for what he wanted to do). Later in the final showdown between Blud and Dark, which logic would imply would happen along the same time, Blud makes a black hole that sucks in not only the world but the rest of the universe as well. This would mean that the future future would not exist anymore.
While it is unclear exactly how Khaos's kontinued existense prevented Blud from destroying the universe, the presence of a future clearly shows that it did. So yeah, Nice Job Breaking It, Hero