Backstabbed in a Backwater Dungeon

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 (信じていた仲間達にダンジョン奥地で殺されかけたがギフト『無限ガチャ』でレベル9999の仲間達を手に入れて元パーティーメンバーと世界に復讐&『ざまぁ！ 』します！) is a Japanese light novel series written by Shisui Meikyō and illustrated by tef.

The series started serialization on the online platform Shōsetsuka ni Narō in April 2020 and was later acquired by Hobby Japan for a print release in May 2021, with a manga adaptation by Takafumi Ōmae being published by Kodansha since May 2021. Both series were licensed for an English-language release, with J-Novel Club publishing the light novel series and Seven Seas Entertainment publishing the manga series.

The series follows Light, a human adventurer who was member of the adventurers group "Gathering of Tribes" in order to fight discrimination against human race. One day, Light was betrayed by his fellow group members left to die in a dungeon called the Abyss. Infuriated by this act, Light swore to take revenge against them for betraying and leaving him behind.

Premise
The world is inhabitated by nine tribes: Dragon people, demons, ghouls, dwarves, elves and dark elves, beast men, centaurs and lastly humans, with the latter ones being the weakest of all. Even though, there are humans which receive a special power, known as "gift", once reaching the age of 10 years.

Light is a human adventurer bestowed with the gift of "unlimited gacha" allowing him to summon an endless amount of cards to support his comrades. He is a member of the Gathering of Tribes, an adventurer group consisting out of dragon kin Draggo, the elf Sasha, the dark elf Shion, beast man Garuu, the dwarf Naano, the centaur Center, the ghoul Diablo and Oboro from the demon race. Seemingly, the group was formed to fight against the discrimination against humanity.

One day, when Light had to be saved in the world's most dangerous dungeon known as the "Abyss" the members revealed to Light that he is no longer a member of the adventurers group and the sole purpose of the group was observing him for being a potential "master" candidate. It is said that the master is a being with the power of overruling the world and destroying civilization. As Light only was able to summon useless cards they decided to classify him not as a threat, to get rid of him and disguise his death as a monster ambush. Before Garuu was able to hit the final blow Light managed to activate a teleportation trap by accident which transports him to the deepest part of the dungeon. As his wounds attracts the attention of numerous monsters he uses his gift in frustration in hope to summon something to distract the threat. He summons the seeker maid Mei, a SUR card, who is able to defeat the monsters with only one blow. Mei reveals to Light that he was able to summon her due to the density of magic in this place and that his summons until now where useless because of the lack of magic on surface. On her question how he was able to reach the deepest part of the dungeon to summon her, Light told her his story of how he was betrayed and nearly killed by his former comrades. Hearing this, Mei offered to support him in his plans to take revenge on those who betrayed him.

For the next three years, Light spends his time and power to build an underground base in the Abyss and decides to return to the surface of the world to start his revenge against his former comrades. When on the way to his hometown he has to see it completely destroyed and people being massacred including his parents. He witnessed other races enslave humans, using them in horrendous experiments or killing them just for fun. So, Light decides to enlarge his revenge to all other races to free humans from enslavement and discrimination as well as to search for his siblings who seemingly have survived the attack on his former hometown.

Main characters

 * Light (ライト)
 * A 12-year old human boy with gift of "unlimited gacha" which allows him to summon endless amounts of cards for support. He was a member of an adventurer group called the Gathering of Tribes.
 * One day while investigating the world's most dangerous dungeon called the "Abyss" he was kicked out of the group and revealed that his comrades were observing him and his gift for being a potential "master" candidate by the order of their kingdoms.
 * His hometown was destroyed while Light was absent. His siblings seemed to have survived the attack, so Light has multiple goals to achieve: Searching for his lost siblings, revenge against his former comrades and finding the truth behind the plan on killing him.

SUR cards Lvl. 9999

 * Mei (メイ)
 * SUR card "Lvl 9999 Seeker Maid Mei" (レベル9999 探求者メイド). She is the first SUR card Light has summoned. She has long, black hair which is tied to a ponytail. Mei is Light's maid and has sworn loyalty to him.
 * In the beginning, Mei has trained Light so he was able to raise his own Lvl to 9999 even though it is believed that the level cap for humans is about 100.


 * Aoyuki (アオユキ)
 * SUR card "Level 9999 Genius Beast Tamer" (レベル9999 天才モンスターテイマー). Aoyuki is the second SUR card summoned by Light. She has a childlike figure and blue hair. Aoyuki wears a hoodie with cat ears. As her name suggests, Aoyuki is capable to control monsters regardless of their levels and amount.


 * Eri (エリー)
 * SUR card "Lvl. 9999 Forbidden Witch Eri" (レベル9999 禁忌の魔女エリー). A beautiful woman with long, blonde hair wearing a witch hat. Eri is the third SUR card which was summoned by Light's gift.
 * As her title suggests, as forbidden witch Eri has mastered magic, wizardry, the dark arts and ghost magic. Eri is capable in creating new spells and to suppress the magic of her opponents.


 * Nazuna (ナズナ)
 * SUR card "Lvl. 9999 True Vampire Knight" (レベル9999 真祖ヴァンパイア騎士（ナイト）). Nazuna is a beautiful young woman with fire-red eyes and long, silver-colored hair. She wears heavy armor and is rumoured to be the strongest warrior in the world. In battle she mostly uses a broadsword which is taller then Nazuna herself.
 * Nazuna is the fourth and last SUR card summoned by Light which is why she is treated like a daughter by the others which led her to develop a childish character.

UR cards Lvl. 7777

 * Suzu (スズ)
 * UR card "Lvl. 7777 All-Rounded Gunner" (レベル7777 両性具有ダブルガンナー). A young girl with violet-colored eyes and short, black hair. She is a gunner carrying a talking musket called "Lock" with her.
 * As Suzu is a timid and silent person, Lock is the one communicating with others on her behalf. However, when provoked, namely by someone insulting Light, she becomes incredibly bloodthirsty and unreasonable.


 * Mera (メラ)
 * UR card "Lvl. 7777 Chimera" (レベル7777 キメラ). A tall woman with red-colored eyes and jagged teeth. She is a chimera whose body consists out of countless other creatures. Mera can cut off parts of her body and put them back together.


 * Ice Heat (アイスヒート)
 * UR card "Lvl. 7777 Grappler of Ice and Heat" (レベル7777 炎熱氷結のグラップラー). A young woman with two-colored hair (red and light blue) which are tied to twintails. As her name suggests, she has high affinity using fire and ice magic. She is capable to summon mythical beasts like Ifrit.
 * She is trained by Mei to be a maid which is why she sometimes wears a maid dress.


 * Jack (ジャック)
 * UR card "Lvl. 7777 Body of Steel" (レベル7777 鋼鉄のボディ). A muscular young man with green eyes, brown-blonde hair and beard roots. Proud of his strength he fights his opponents with his fists instead of using a weapon. He can envelop his body in a suit of material which is stronger than steel.

Lvl. 5000

 * Gold (ゴールド)
 * UR card "Lvl. 5000 Golden Knight" (レベル5000 黄金の騎士). A warrior wearing a golden armor. Together with Light, who disguised his identity using the pseudonym "Dark" and the assassin, Gold forms the adventurer party called the "Masked Clown".
 * Gold is loyal towards Light and shares his knowledge as a warrior with other adventurers. He and Nemumu are teasing each other on a regular basis. Giving the impression that Gold and Nemumu can't stand each other, Gold cares for his companions.


 * Nemumu (ネムム)
 * UR card "Lvl. 5000 Assassin Blade" (レベル5000 アサシンブレイド). A young woman with short, white hair. As an assassin, Nemumu is capable in sneaking up towards her opponents without being noticed. She has high affinity in using knives and creating the strongest poisons. She can inculcate her surroundings by using a scream in ultrasound range.
 * Together with Light and Gold she is part of the "The Masked Clown" adventurer group which was formed to investigate the surface of the world and the other races in search for clues on the "master". Like Gold, Nemumu is loyal towards Light which she shows in kissing his feet even to his embarrassment. She is often teased by gold for her figure.

Gathering of Tribes

 * Draggo (ドラゴ)
 * A warrior from the race of dragon people. His level is 512. Draggo is the leader of the adventurer group "Gathering of Tribes" which Light was part of. Even when he looks like a prudent and friendly person, Draggo was the one who ordered the others to kill Light and disguise the murder as a monster attack.


 * Sasha (サーシャ)
 * An archer from the elven tribe. Her level is 308. She was born as a result of an affair between a nobleman and a commoner which is why she was disowned by her family.
 * She seemingly had feelings for Light which turned out to be a lie which is why the other members of the Gathering of Tribes mocked her.
 * After seemingly killing Light and her engagement with a high-ranked elf her reputation within her race and family risen up. When she was made aware that Light is still alive she tries to kill him in order to keep her reputation.


 * Garuu (ガルー)
 * A warrior from the beast men tribe, Garuu is a wolf man who fights his opponents with his claws. His level is at 151. Garuu was ordered by Draggo to hit the final blow on Light. Before Garuu can kill the young boy, Light escaped activating a teleportation trap by accident.
 * After Light was declared dead, Garuu became popular among the beast man tribe. In reality, Garuu is a coward and would betray his own friends in order to survive. As his tribe is one of the weakest (with only humans being weaker), he has no information regarding the mission of the "Gathering of Races".


 * Shion (シオン)
 * A young woman and researcher from the dark elf tribe at level 304. Shion is considered a prodigy and was able to graduate at a renowned university where people from all races can study without facing discrimination.
 * She became a professor at the university and was fired after it was discovered that she used humans for her researches on the "gift". The loss of her professorship and her source of income, she decided to work as an adventurer and was soon scouted to become a member of the "Gathering of Tribes".
 * To her, her research has the highest priority which is why she shows no emotions, neither towards humans nor to her own tribe. She is willing to sacrifice each and everyone as long as she can accomplish her goals in her research.
 * Shion made a pact with a soul dragon, a monster from another world in hopes to reach her goal. Her character was added in the manga.


 * Naano (ナーノ)
 * A smith from the dwarven tribe whose goal is to create a godlike weapon. His level is 301. Due to his fame he was chosen by the dwarven king to join the "Gathering of Tribes" to observe Light and his gift.
 * After the mission was accomplished, Nano became addicted to alcohol because he failed to reach his own goal and was denied for a second chance to look for the "master" which he blames Light for.
 * Naano tests his forged weapons on humans. On day he received a instruction for smithing a seemingly holy weapon by a mysterious merchant.


 * Center (サントル)
 * A warrior from the centaur tribe whose level is at 152. His character was added in the manga.


 * Oboro (オボロ)
 * A fighter from the demon race who is at level 403. His character was added in the manga.


 * Diablo (ディアブロ)
 * A ghoul warrior at level 419. His is the second strongest member of the "Gathering of Tribes" right after Draggo.

C's Group
C is a mysterious being that made themselves known while Light was dealing with Naano. Not much is known about C, except they know about Light's quest for vengeance and it's implied by Kaava that C is a Master.
 * Kaava: Known as the Level 5000 Flesh Zombie, Kaava is a human with the ability to boost his abilities by eating human flesh.

Terminology

 * Gathering of Races
 * The "Gathering of Races" is the name of the adventurer group, Light was a member of. The group consists out of six members from different races. In the manga series, three new characters were introduced as part of the group.
 * Races who are weak according to their levels are despised and enslaved by the stronger tribes. The group was seemingly started and recruited by fighters from all races to fight against the discrimination.
 * In reality, the group was formed to find an existences which is known as "master". The goal of each tribe is to win over that very existence. Light, who was bestowed with a rare gift was invited to join the group because of speculations that he might be the existence everone is searching for. Once it was seemingly clear that Light is not the "master" it was decided to kill him and disguise his murder.


 * Master
 * The "master" (ますたー) is an existence all tribes are looking for and the very reason why Light was almost killed. It is that that the "master" has the power to change the world or even to destroy civilizations.


 * Level cap
 * The level cap indicates to which point an individuum can reach strength. Usually, the level cap for humans is at 100, 200 to 300 for beast men, 500 for dwarves, 300 to 1,000 for demons and 1,000 for elves and dragon kin.
 * Each society believe that these are the common level caps, even though it is unclear if these are correct. It is also believed that those races which has blood a master in their veins can easily break those limitations.


 * Gift
 * A rare power which is bestowed to a few humans once reaching a certain age. One of those powers is "unlimited gacha" which allows the user to summon an endless amount of cards for support. Those summoned cards have different rarities which ranks from EX (Extra); SUR (Super Ultra Rare), UR (Ultra Rare), SR (Super Rare), R (Rare) and N (Normal).

Light novels
Shisui Meikyō began writing the series as a web novel and started publishing the chapters on Shōsetsuka ni Narō on April 17, 2020.

Japanese publisher Hobby Japan acquired the rights for a print release of the series and started publishing the novel under their HJ Novels imprint. The light novel, written by Meikyō and illustrated by tef, was published in physical format with the first volume released on May 19, 2021. As of March 2024, nine volumes have been published.

In July 2022, American publisher J-Novel Club announced to have licensed the novel series for an English-language release.

Manga
Takafumi Ōmae started a manga adaptation of the series in Kodansha's Magazine Pocket website on May 25, 2021. The first volume of the manga was released in print on August 6, 2021 in tankōbon format. As of May 2024, twelve volumes have been released.

In May 2022, Seven Seas Entertainment announced to have licensed the manga for an English-language translation.

Chapters not yet in tankōbon format
These chapters have yet to be published in a tankōbon volume.
 * Chapters 93-132