Hell's Heroes (2009) (edit title/settings)

Taken from wikipedia
The novel begins with Grubbs and Dervish talking in a cave. The wounded Dervish is awaiting his imminent death, but he and Grubbs take it in their normal humorous stride. Grubbs reflects on how Dervish has always been there for him and begins to recall memories of his time with his uncle. Dervish dies during Grubbs' reflections. Grubbs takes his body into the open air and begins the slow, painful process of digging his uncle's grave.
The story then moves on by a month. Grubbs has been fighting wave after wave of demons that are breaking through all over the globe. He has gathered another group of werewolves but is slowly being worn down. He has been having a recurring dream of Lord Loss's kingdom, but one night it changes and he sees Lord Loss and Bec’s souls go into the Earth’s first chessboard. When they reappear it seems that Bec has made a deal with Lord Loss, and this assures Grubbs that Bec has betrayed them. This spurs him, Kernel and Kirilli Kovacs to action (even though Kernel would rather not); in the dream it seems that Bec is going to show Lord Loss the locations of lodestones so that they can create a tunnel between universes. Therefore, they decide to destroy as many lodestones as they can before Bec can get to them, and go to the only lodestone whose location they know, the one at Carcery Vale.
When they get there, they walk around Dervish's old mansion for a while, and then reopen the tunnel to the lodestone in the forest. Grubbs smashes the stone against the wall, so that it cannot be used. As they are about to leave Shark (an ex-soldier and Disciple) and Timas Brauss (a slightly weird computer genius) come in. After quite a brief conversation they decide that they should go to face Lord Loss and Bec on their home turf, but Grubbs says that Kernel can leave if he wants. Grubbs is able to open a window to a world that they know is safe, and Kernel starts to rebuild his eyes. Before he finishes, another window opens. Demons pour through and reawaken the demon master in that world, forcing them through the window to Lord Loss's realm. They confront and battle the demon master and Bec, and their former ally reveals that she has indeed decided to work with Lord Loss. When they have stopped fighting Lord Loss reveals thousands of humans in the rooms around them whose souls have been trapped in the original chessboard. As they watch, Bec kills everyone in the board and releases Death who shares its body with Bec. Kernel completes a window and the others follow narrowly escaping the new Deathly-Bec.
Kernel realises that now that Death is back on the scene there is no hope for the Earth, so he decides to go back to the 'Ark' to save a small part of the life from this universe. Kirilli has the idea to get the Old Creatures to help protect the Earth, so Grubbs agrees to the plan. When Kernel has opened a window, they decide that only Grubbs and Kernel should go to meet the Raz(the Old Creature that Kernel has met before). Grubbs begins to make the request to Raz, but, having read his mind, Raz states that the Old Creatures will not help. As Grubbs is about to go home, another window opens and Deathly-Bec comes through, explaining that she can go anywhere Kernel has been, and that she knows where the 'Ark' is. She then attacks and kills Raz, but this drains some of Death’s power, and she regains enough control of herself to shout at Kernel and Grubs to get away before Death kills them and can reunite the Kah-Gash. They do as she suggests and return to the others, but Grubbs is now suspicious that Bec is not as evil and demonic as they thought.
They resign themselves to the end of the world, but decide that they should try to kill as many demons as they can before the world falls. When they go back to Earth, the world is being besieged by demons, who have managed to open a tunnel. They decide that they might as well try to close the tunnel and forestall the annihilation of Earth. They fight with a new vigor (even Kernel, who didn’t like the fighting, has decided that there is nothing to lose anymore), make it to the tunnel entrance and destroy the lodestone, causing the demons to be sucked back to their realm. However, this is just the first of many tunnels that are going to open, so the team decide to just go for the tunnels that threaten the world as a whole, and leave the ones that can only cover a few hundred kilometres.
After four days Kernel sees the lights going wild, the sign that a tunnel of great power is opening. A team fronted by Grubbs, Kernel, Kirilli, Shark and Timas go to the edge of a cliff where the tunnel is (this is the place that Bec and Beranabus travel to in the fourth book and where we see the Old Creatures for the first time). Grubbs uses the power coming through the forming tunnel to re-enact Moses and the parts the sea, and then creates steps down to the cave and tunnel. Timas stays on top, and he and Shark inform the others that they have arranged for nuclear devices all over the world to be detonated if the team fail, therefore causing the humans to be killed instantly, instead of waiting for the demons to torture them.
On the way down the Kah-Gash informs Grubbs that it never wanted to manipulate them, and isn't working for the demons or humans. This means that Grubbs can use the ancient weapon as much as he wants, and it will do whatever he wants. When they go in, they find the tunnel entrance and Lord Loss and Deathly-Bec waiting for them. While the tunnel is opening, a fight breaks out, and Grubbs manages to catch Lord Loss by surprise using his and Kernel's parts of the Kah-Gash, taking him out of action for a while. The pair begins to seal the tunnel again, but then Bec steps in. She diverts Kernel and Grubbs's power into herself, giving the masters in the tunnel the opportunity to burst through. This is when Grubbs realises that Lord Loss, who he has been afraid of since his parents and sister were slaughtered, was only one of the lesser demon masters, and that the ones that are pouring through at the moment are many times stronger than him.
In the following fight Kirilli is decapitated then carved into many pieces, and Shark is melted along with most of the other werewolves and soldiers. In a last attempt Kernel and Grubbs grab Bec to try to blow her up in the tunnel to close it, but when they get her to the mouth of the tunnel and direct all their energy into her, nothing happens. Bec begins to control the weapon, and in a last attempt to stop her, Grubbs cuts the flow of energy to her, but then she winks at him. This catches him by surprise, and he quickly makes the decision that she wasn’t trying to fool him, so instead of cutting the power to Bec, he increases it, directing all the power around them into the girl. The Kah-Gash becomes fully active, and starts a similar process as it did in the sixth book, but at much more advanced stage. They begin to rip everything in our universe and the Demonata’s to shreds, Bec then tells them to go to the Crux (the place where both universes expanded from), and reveals that she is following a plan devised by Beranabus. When they arrive at the Crux, they split into sixty four pieces, and slot all of the body of the Kah-Gash back together. The original universe is back in place, with the Demonata in the Black zones and the Old Creatures in the white zones.
Bec has restored the old universe, but now the Kah-Gash has the three teenagers as a mind. Bec explains that because she is the Kah-Gash’s memory she memorised everything as they destroyed it, so that now the three of them can rebuild the human universe exactly as it was. Grubbs believes that now that they have restored the old universe, everything will happen as it did before, the Kah-Gash will split, and everything will repeat itself if they recreate everything, but Kernel realises what the next part of the plan was. As they now hold the universe together, they hold everything inside together, including the demons. This means that they can easily undo those bonds and destroy the demons. However, Bec persuades them out of destroying every demon, and Kernel shows them a clip of the past where Beranabus tells Grubbs that most of the demons are not worth bothering about. This sways Grubbs into the others’ way of thinking, and the three decide to destroy all the demon masters who have the potential to cross, leaving only one until last.
Having decided to kill Lord Loss personally, they reform their bodies and meet the last master. As they go to kill him, Bec stops them, revealing that she had made a deal with Lord Loss in the chess board: he would protect Bec if she would spare him. After an argument, they realise that Bec's other reason for sparing him was to let him be the necessary diabolical figure feared by the recreated beings of the universe. It is revealed that he will now be set to rule the Demonata, making sure that everything happens as it did before. It is also to be noted that Lord Loss admits that the universe(s) would be a better place without the stronger demon masters.
The poem that Darren Shan wrote (which inspired this series and is in the front of Lord Loss) is repeated.
The trio then leave Lord Loss, choose a black square at random and prepare to restart the human universe with the Big Bang therein, making sure that everything is as it was the first time. However, they decide that everything will not be exactly as it was before; to stop our world falling to the Demonata again, they will have to change history. Choosing a point just before Bec was born, they intervene to prevent the series of events which led to Death developing a consciousness. Grubbs also wishes to make a few more tweaks, such as letting his parents live and giving Dervish a stronger heart. The three decide that they will spend more time discussing how much they should change, and the extent of their alterations is therefore not explicitly stated. They also decide, to appease the Old Creatures, to retain the original universe alongside the new human universe. Since this time the Kah-Gash makes the conscious decision to create the Big-Bang, instead of a result of the demons crossing through the zones of the Old Universe, Grubbs, Kernel and Bec can retain the Old Universe and leave the Old Creatures to live in their zones.
As the trigger of the Kah-Gash, Grubbs then has the job of starting the Big Bang. The series ends with Grubbs saying a slightly changed biblical quote:
"In the beginning Grubbs created the Heavens and the Earth and everything was dark. Then Grubbs said 'Let there be light' "
"And there was light."
Coolio!