The One Sin

"Damage done to the evil-shaped one too massive to compare..."

- W.B. Yeats

The One Sin (ザワン・シン) was known as The World's "unbeatable" event. Many players have tried and failed to complete it. It was finally conquered by Balmung and Orca, who would be later hailed as the Descendants of Fianna.

The Field
Located in Ω Sickened Imprisoned Fallen Angel, the field was unique. It lacked a map and music, and was covered with a blinding snowstorm. This combination meant that players trying to challenge the field would be easily ambushed by the field's high-level monsters. In the center of the field was a mountain of ice with stairs carved into one side. At the peak was the eponymous fiercest boss, The One Sin.

The One Sin
The One Sin (sometimes described as a "spectrum dragon") seemed to take absolutely no damage while it dealt lethal damage with every blow. On top of that, its HP totaled at 65,536. The only way to cause damage to it is to attack whilst it is using an elemental attack and, even then, only an attack of the opposing element can damage it.

The One Sin is a boss that counters every attack by using the same element used against it. Because the average player's first instinct is to attack, few people would actually see its pattern of attack.

Reward
The destruction of The One Sin meant the release of a captive angel (hence the field's keywords). The field would then become a normal field with no snowstorm or ice mountain.

According to .hack//AI Buster, Balmung was the one who delivered the final blow along with doing the most damage, making him the MVP and giving him the reward of a unique character edit. Balmung used this reward to gain his wings.

Revival
The One Sin quest appears once again in The World R:2. This time the monster appears at Dark Morrigu Barrow Wall, on the opposite side of Morrigu Barrow Wall. Being a Lost Ground, this area may bear some connection to the field in The World. The One Sin initially has only two crests, allowing it only one fourth of its power and the ability to control only the elements light and dark. After being defeated however, it comes back as God Eater, a much stronger version of The One Sin. This campaign may extend further as The One Sin regains its powers, though since The World R:2 contains eight elements in total, it would be significantly more difficult than its predecessor with all the crests.

In the Forest of Pain, an even more powerful version of The One Sin known as The One Death is summoned on Floor 70.

The World R:2 Official Story
The One Sin was another weapon used by the humans to destroy the gods. It gained its immense power by drawing in energy from its surroundings.

The World R:X(.Hack//QUANTUM)
In .Hack//Quantum, one of the largest events is taking down 'The One Sin', also noted as the Unbeatable Monster of The World in this revision as well, interestingly enough, however, he was not a Spectrum Dragon like his description. Instead, he was a rather large, demonic looking Dragon and further pushes this point when he is infected by Hermit. When players came to fight him, however, instead of the two person party Balmung and Orca had, or the 3 person party Haseo and team had, it took 3 full raiding parties of at least 8 to 10 players in each party, meaning this iteration may either be the strongest of all One Sin variations, or that his strength was over-played in Quantum.

Trivia

 * The field of the One Sin event, Ω Sickened Imprisoned Fallen Angel, is a special field in .hack//QUARANTINE. Aside from Data Bugs being found within it, the Gott Statue at the bottom of the dungeon has the one-of-a-kind item "Risky Coffee" which restores HP and SP to full.
 * The One Sin was improperly romanized as "Zawan Shin" in Tokyopop's first edition of Legend of the Twilight Volume 3. Although it technically is a correct romanization, the form has no meaning. This error was fixed in later printings of the book.
 * In the Japanese version of AI Buster, two distinct Japanese meanings for the English are given: "The One Sin", and "The One Thing", playing on the ambiguity of the sound. According to "Tell Me Mr. Piroshi!", both are legitimate meanings of the name.
 * In the Japanese version of Reminisce, "God Eater" was called "The One Godeater".
 * In the English version of .hack//AI buster, the final attack from Balmung that defeated The One Sin dealt 65,536 points of damage, far beyond the regular damage cap of 9,999 (the only other attack that can break the damage cap is the Death ability when used against a Data Bug). This, however is a mistranslation. In the Japanese version, Balmung merely struck the last of its 65,536 HP.