Guren SEITEN Eight Elements

The Guren S.E.I.T.E.N. Eight Elements (紅蓮聖天八極式) was upgraded from the Guren Flight-Enabled Version after Kallen and the Guren were captured during a battle with the Chinese Federation and turned over to the Holy Britannian Empire, after which Lloyd and Cécile were given access to the Guren. Much like Rakshata and the Shen Hu, they got carried away in their modifications and made it too difficult for ordinary people to pilot properly. The Guren S.E.I.T.E.N. Eight Elements was later recovered by the Black Knights, along with Kallen, during the Second Battle of Tokyo.

Design and development
Having been reconfigured by Camelot, the Guren was rebuilt as the world's first 9th-Generation Knightmare Frame. It became the first KMF to employ the use of the Energy Wing System that would later be incorporated into the Lancelot Albion, but with four energy "feathers" instead of three on each wing. The feathers are capable of functioning as blades, shields, and projectiles. The system allows the Guren to move at blinding speeds, such that it appears to be little more than a purple blur in flight. Its Radiant Wave Surger arm now has gold highlights on the fingers and forearm, and has been heavily upgraded from its previous form. It can be fired like a Slash Harken, with a Harken Booster for controlled flight. The arm continues to function while separated from the main body. While the RWS can still fire at long-range as it did with the Flight-Enabled version, the S.E.I.T.E.N. is now capable of launching a disk-like energy projectile. It has also been newly equipped with two Slash Harkens which are attached to its shoulders.

All of the Guren’s original functions are retained and upgraded. The regular short-range radiation burst can now block even a Hadron blast, while the hand can crush energy shielding without the aid of the emitter. The Surger arm is also equipped with 4 rods that can be closed around the hand, able to deliver an attack strong enough to pierce the Albion's armor. The Guren’s Fork Knife is also upgraded, having been retrofitted with MVS capability and doubled in length. The power of its MVS is more potent than most MVS weaponry, as shown by its purple coloration, as opposed to the typical red. The knife is used to cut through the Lancelot Conquista’s MVS swords and even shatter the Percival’s Particle Lance, which was built using Blaze Luminous technology.

Additional armor has been added to the knees and ankles, and the antennae have been extended and enlarged, giving them the appearance of giant ears. The torso has been remade, with the orange section extended further outward and a pair of green jewels featured prominently on the front, causing the section to somewhat resemble a bird’s head. Its namesake comes from its operation system, the Superlative Extruder Interlocked Technology Exclusive Nexus (S.E.I.T.E.N.) Eight Elements.

According to Lloyd, a capable devicer (like Kallen) can destroy 8th generation and below Knightmares even at 60% of its total output. In the scientist's own words, "With a capable devicer, even at 60% output, that thing can cut the other Knightmares to ribbons!"

Operational history
The Guren S.E.I.T.E.N. is first seen after Kallen is freed from prison during the Second Battle of Tokyo where it is shown to her by her rescuers. Despite being supposedly being made too difficult to pilot by Lloyd's tinkering, Kallen manages to pilot the upgraded Guren and with it quickly turns the tide of the battle, destroying countless Britannia Knightmares as well as single-handedly defeating the Valkyrie Squadron, Knight of Ten Luciano Bradley in his Percival and severely damaging the Lancelot Conquista to the point that Kururugi's "Live" command activates and forces him to use F.L.E.I.J.A. Kallen and the Guren escape the blast however and retreat with the rest of the Black Knights.

The Guren’s final deployment is during the Battle of Mt. Fuji. During the battle, Kallen attacks the Avalon with the Guren in an attempt to kill Lelouch, but is stopped by C.C. in the Lancelot Frontier. After quickly defeating C.C., Kallen soon challenges Kururugi in his Lancelot Albion and the two begin an intense duel. During the fight, both the Guren and the Lancelot ran out of sufficient amount of energy to power most of their systems, including the Energy Wing, forcing them to battle aboard the Damocles. After more intensive fighting, both Knightmares delivered their last blows, the Lancelot being completely destroyed and the Guren losing its arms and head before plummeting from the Damocles after Kallen falls unconscious. However, it is caught by Gino in a damaged Tristan Divider. It is not shown what becomes of the Guren following the Zero Requiem, though presumably it was returned to Rakshata.

Trivia

 * The term S.E.I.T.E.N. is an acronym for "Superlative Extruder Interlocked Technology Exclusive Nexus".
 * The word that the acronym forms can be roughly translated to "sacred heaven" or "equaling heaven". This fits into the machine's place in the story as, at the time of its debut, the Guren S.E.I.T.E.N. was the planet's most powerful and technologically advanced Knightmare Frame.
 * In the climax of Re;, Kallen states that the Guren S.E.I.T.E.N. technically has greater specs than the Lancelot Albion. If so, then the S.E.I.T.E.N., technically speaking, was the series' most powerful Knightmare not only at its debut, but also for the remainder of the original series.