Alternative Character Interpretation: It's implied near the end of the book that Jacobs was already going down the path of madness prior to his wife and son's deaths, and may have experimented on both of them as well. And that said experiments indirectly led to their deaths in the first place. Rather than being motivation, seeing his wife and son again is just an excuse for Jacobs to push ahead with his experiments.
Moment of Awesome: During the climax, "Mother" comes through the resurrected Mary Fay and tries to break Jamie. He defies her and fires at Fay's corpse, cutting off "Mother" before she can enter the world. However, this is then horrifically subverted when Jamie's act of defiance prompts "Mother" to drive several of the people Jacobs "healed" to murder and suicides—immediately, that is. Over the next few years, hundreds more follow suit.
Moral Event Horizon: Jacobs crosses this with the various experiments performed on those he "healed". In-verse, Jamie believes he's crossed this line when a boy he "healed" went insane, was institutionalized, and committed suicide.
The death of Jamie's sister, Claire. She got into a bad relationship with an abusive monster, and managed to escape him — only for the abuser to attack her at a school and kill them both in a murder-suicide.
There are also the deaths of Patsy and Morrie, which drive Jacobs over the Despair Event Horizon. Especially awful is Jacobs's reaction to what happened: "Where's his face? Where's my little boy's face?"
There's also the revelation that everyone after death is forcefully abducted and forced to slave away for "Mother" and other monsters by vicious antlike beasts.
Revival's Big Bad "Maya Lottie", aka Nyarlathotep, is the most active and personable of the Outer Gods. Having grown bored with the usual games he plays on mankind, he decides to bring an end to existence to give the world a final curtain call. Previously driving an entire town to madness and death, Nyarlathotep devours the family of Patrick Stark, taking the form and alias of his daughter Maya to spite and enslave him. He starts by killing the Loud family dog, and gives Lana the Necronomicon to resurrect him, having her invoke the Old Ones. Attacking the Loud family, Nyarlathotep sets his army onto Royal Woods, killing hundreds alone; drives both Loud parents out of their minds; forcibly takes Leni and Lola's souls to bargain with the Louds, flinging them into space-time; he then summons the pantheon onto the world, slaughtering thousands of people. Nyarlathotep makes a deal with Lincoln to call things off if the latter could save his sisters' souls, not intending to hold his end of the deal if Lincoln wins; he tries to cheat when Lincoln starts to win, summoning Cthulhu to kill the Loud sisters, and forced the Louds into a final confrontation. As he dies, Nyarlathotep's life flashes before their eyes, revealing the great atrocities he was involved in throughout history.
Yog-Sothoth is one of the highest-ranking and seemingly omnipotent Outer Gods, who looks down on everyone and sees Nyarlathotep's attempted apocalypse as the time to take the universe back from lesser beings. Yog-Sothoth decides to pick up where Nyarlathotep left off by attempting to destroy the world before being banished, during which he attempts to kill the Loud siblings by erasing them, from youngest to oldest. Returning in the sequel, Yog-Sothoth takes the form of a female humanoid and kills Cthylla by ripping the reincarnated Cthulhu out of her womb. From there Cthulhu—essentially reduced to an innocent child—is raised by Yog-Sothoth to face Hastur; these methods include having the infant Cthulhu constantly attacked and mutilated by monstrosities, always stopping short of death; as well as forcing him to slaughter the loyal, sapient Deep Ones, who raised him as family. Teaming up with the Louds to stop Hastur, when the latter is defeated, Yog-Sothoth reveals his true intentions is to use Cthulhu as a weapon and bring about a new apocalypse of his own.
Hastur, from The King in Yellow, the envious and hateful half-brother of Cthulhu, is portrayed as an arrogant but weak god who thinks he's entitled to the world. Seemingly killed when humanity fought back against him, Hastur seeks out Cthulhu's daughter Cthylla, planning to kill her and prevent Cthulhu from interfering with his plans; to that end he wipes out a civilization of Deep Ones trying to protect her. Recovering in Royal Woods, Hastur forcibly twists and mutates helpless victims into his slaves, often killing them at the smallest slight. Hastur plans on spreading his sign across the world to force this fate onto everyone, and recruits Dr. Moist into his plans, needlessly slaughtering his staff. Hastur arranges to have Lisa Loud kidnapped to have her create a device that would broadcast his sign around the world, and tries to drive her mad by revealing his face. When the broadcast begins, that alone causes mass death and destruction; the second part of his plan is to torture Nyarlathotep's daughter Mia into ushering in the pantheon to tear the universe apart.
