Backstabbed in a Backwater Dungeon: My Trusted Companions Tried to Kill Me, But Thanks to the Gift of an Unlimited Gacha I Got LVL 9999 Friends and Am Out For Revenge on My Former Party Members and the World (Light Novel) Series

Light’s revenge tour takes him to the Elven Queendom, home of his former partymate Sasha. Her reward for leaving him for dead was riches, status, and a betrothal to Sir Mikhael, second-in-command of the queendom’s elite White Knights. To “congratulate” Sasha on her engagement, Light issues her a challenge: face off against him in a giant tower shaped like a wedding cake! Although Sasha knows it’s a trap, she must rectify her former party’s mistake of leaving Light alive three years ago in order to preserve her new lifestyle. With Sir Mikhael and the White Knights in tow, she challenges Light and his crew of Level 9999 bombshells—plus a few new faces. Can they overcome the might of one of the world’s strongest nations?

When Light is kicked out of the Concord of the Tribes, his former comrades instantly turn on him. Light escapes this diabolical act of betrayal by the skin of his teeth...only to find himself in the deepest part of the Abyss, the most dangerous dungeon in the realm! To avoid being eaten by carnivorous monsters, he uses the Unlimited Gacha, his sole magical skill. But where it previously only produced junk items, this time Mei—a gorgeous Level 9999 fighter in a maid outfit—springs forth! Fast forward three years and Light has carved out his own kingdom in this backwater dungeon, summoning more beautiful Level 9999 warriors who swear absolute fealty to him. Now a powerful Level 9999 Overlord himself, Light plans to ascend to the surface and take revenge on his betrayers one by one!

Fresh from getting revenge on the elf who put an arrow in him on that fateful day, Light learns that another of his betrayers, the dark elf Sionne, is in grave danger. While conducting experiments on Gifted humans in her underground lab, she accidentally summoned a soul-eating dragon that has transformed her lab into a vast dungeon. Light now has no choice but to rescue her if he wants to get even with his old foe. So, in his guise as leader of the Black Fools, Light teams up with a party of dark elves led by Yude, a high-ranked adventurer who’s taking point on a quest to wipe this new dungeon off the map. But there’s more to Yude than meets the eye, and Light soon finds out that this potentially world-destroying dungeon isn’t the only threat he’s up against. Can Light navigate the liminal space between the worlds of the living and the dead to get revenge on Sionne before she dies some other way?

After crossing Sionne off his revenge list and sealing the tremor-causing interdimensional portal for good, Light returns to the Abyss, where his debrief is interrupted by news from Mei. She tells Light they’ve found his younger sister, Yume, who went missing after someone—or something—destroyed their hometown. It turns out she is still in the Human Kingdom after being rescued by Princess Lilith, who kept her on as a maid. While Light makes plans to bring Yume to the Abyss, he reminisces about his life since they last saw each other. He recounts the days after he was betrayed, going from merely surviving the Abyss with Mei to pushing past his limits, summoning more overpowered allies, and eventually transforming the world’s more notorious dungeon into his very own hidden kingdom. When Light finally meets Princess Lilith himself, they find they share a passion for improving humanity’s lot—but a dark secret plagues her kingdom.

While Light was busy clearing the Abyss of monsters so that he had somewhere to build his new kingdom, his former Concord of the Tribes cohort, Naano, was slowly slipping deeper into despair. Despite being showered with riches and securing a top job in the Dwarf Kingdom’s most distinguished smithy, the talented blacksmith felt the course of events was taking him further and further from his life’s goal: to craft the ultimate legendary weapon. However, an encounter with a human merchant puts him on a new, much darker path to fulfilling his dream, and with his goal now in sight, Naano will stop at nothing to craft a legendary sword, even if it means spilling the blood of countless innocents. Meanwhile, Light’s quest for revenge on Naano leads to him striking a deal with the ruler of the Dwarf Kingdom, King Dagan, but will aiding him to explore some vast, labyrinthine ruins replete with deadly traps and powerful guardians from which no one has returned prove to be an unwise undertaking?

For Light and his allies in the Great Tower, the war with the Beastfolk Federation proved to be little more than a bump in the road, but the repercussions turn out to be more of an issue than originally assumed. News of the tower’s overwhelming victory spreads around the world like wildfire, making a number of the other nations sit up and take notice, and causing the next multinational summit to be brought forward as a matter of urgency. This has the knock-on effect of accelerating the plans of Princess Lilith of the Human Kingdom, who wishes to use the event to overthrow her father and seize the crown so that she can lead her nation toward a brighter future. However, she cannot accomplish her goals alone, so she comes to Light for help. Meanwhile, the manner of the Great Tower’s victory over the Beastfolk Federation’s army attracts the attention of another cabal of powerful Masters, who are quick to send out one of their own to investigate the source of the tower’s remarkable power.

The Masters hosted by the Dragonute Empire have grown increasingly concerned about their lack of knowledge surrounding the emergence of the Great Tower as well as the sudden disappearances of former members of the Concord of the Tribes, so they hatch a scheme to find out who exactly they are up against. Their plan is to get the Beastfolk Federation to declare war on the Great Tower while they watch on from afar to learn about their opponents without the need to reveal themselves. For their part, the beastfolk have their own reasons for going to war with the Great Tower. Light’s lieutenant, Ellie—aka the Wicked Witch of the Tower—has successfully conquered the elves and the dark elves, freeing the human slaves suffering under their heels in the process. Not wishing to share the same fate, the beastfolk are determined to destroy the Great Tower. But how can a relatively weak nation fight a sorceress who has her own personal army of dragons? By fighting dirty, that’s how.