Ries Island Arc

 Ries Island Arc is the fourth story arc of the Saijaku Muhai no Bahamut series. This arc highlights the students' training camp at Ries Island under Relie Aingram's orders and their unexpected exploration of the Ark, one of many Ruins in the world. It also reveals that Philuffy Aingram was a survivor of the Old Arcadia Empire's human experimentation.

Relie's True Goal and The Truth
Relie meets Lux whom is triying to remember the five years ago incident. She should have been saved, by the time he received letter from Relie. Relie explains that it was half-true. Relie and her followers discovered that she had been dead but something strange happened. After that incident, Philuffy s physical ability significantly was tougher, even an adult was no match for her. Relie researched what was going on and entrusted her to other family. She finally discovered that Philuffy became abyss-like. Relie concealed the fact from everybody else. if someone reports to the authority, a death penalty will apply to Philuffy whom is a threat as abyss.

Lux finally comprehend that investigation ruin this time is held unlawfully to save Philuffy.

Anime

 * Some of the scenes from this arc were mixed with the Celistia Arc, especially the training camp and the beach in Ries Island.
 * The island itself becomes the main setting in this and the Celistia arc.
 * In contrast to the Light Novel, in the anime Celis only opens up to Lux after their mock duel that was interrupted by Saniya's betrayal.


 * Three of the Great Nobles suggest that Queen Raffi use the students as the New Kingdom's warriors despite the queen's displeasure and suspicions. One of the students they mention is Lux, who they view to be useful for the New Kingdom's purposes.


 * Fugil didn't confront everyone after Hayes's defeat while Lisha herself was too busy to take care of the already injured and exhausted Lux.

Major characters

 * Philuffy Aingram
 * Lux Arcadia
 * Celistia Ralgris
 * Saniya Lemiste
 * Lisesharte Atismata
 * Krulcifer Einfolk
 * Hayes Vi Arcadia

Supporting characters

 * Relie Aingram
 * Airi Arcadia
 * Four Great Nobles (barring Warg Kreutzer)

Minor Character

 * Fugil Arcadia

Story Impact

 * Ark is introduced as the fourth Ruin of the world, and it is also the second Ruin that is visited by Lux and his friends. It is later revealed as a "reproduction factory" for Abyss that is used by Hayes to wreak havoc across the world.


 * It's revealed that Lux once promised Philuffy that he will make the Old Empire a better place. Unfortunately, he was unable to stop her becoming a subject of the empire's experiments. This played a vital role in Lux's decision to join the coup against the Old Arcadia Kingdom.


 * Lux uses Over Limit to unleash Bahamut's true power and speed, allowing him to defeat a Ragnarok, though he mysteriously forgets how to activate it afterwards.


 * The destruction of Yggdrasil drastically changes those involved:
 * Fugil makes his first present-day appearance in this arc, where he watches Lux and his friends' struggle against both Hayes and Yggdrasil. Lux's narrow victory via Over Limit further drives Fugil to look forward to his former sibling and future rival.
 * Hayes herself has to retreat, but her feud with Lux and his friends continues as she later returns and vows to avenge her humiliation in the next arc.

Trivia
(To be added...)