Demon Dragon Emperor

The Demon Dragon Emperor is the Dragon Emperor fragment of Glass' World.

Gaelion-Possessed Form
As the Demon Dragon Emperor possessed Gaelion, it created a 20 meter high, fully-grown dragon form out of black sludge. It's eyes were filled with darkness. As the sludge solidified, it took on a purple hue. The Demon Dragon's new look reminded Naofumi of his Shield of Wrath.

Post-Revival
After being revived by the heroes, the Demon Dragon Emperor looked like a purple palette-swap of Gaelion. Revived in a female this time, she initially had the same small infantile body with tiny wings and a fat tail. However, the look in her eyes were quite different from either forms of Gaelion. From a glance Naofumi could notice that she harbored a lot of ill-will.

Personality
The Demon Dragon is a vicious, ruthless, and highly intelligent megalomaniac. His desire to rule the world stems from the belief that those who currently run the world are unworthy. Worst yet he thinks nothing about who he has to hurt or make an alliance with in order to secure his own power thinking nothing of taking over the body or the infantile Gaelion or converting Filo and Naofumi Iwatani into sources of power by integrating them into his body.

Powers and Abilities
The Demon Dragon is an expert in the use of dark magic and especially curses, buffing, and de-buffing type magic. His vast affinity for the dragon vein allows him to neutralize incoming magic attacks. He's also shown the ability to manipulate people who have integrated his dragon core into themselves, such as taking control of Filo or locking Naofumi out of the Legendary shield.

His connection to the Wrath shield has given him the defense rating of Naofumi's strongest shield and his fire breath has turned into the Dark Burning curse. He also gained the benefit of Naofumi's beast growth corrections which made his stats much higher than the average dragon.

Background
The Demon Dragon Emperor is a fragment of the Dragon Emperor from Glass' world that tried to take over the said world and subjugate the people. The reason for this is because the Demon Dragon thinks that humans and thus other similar beings are selfish, hateful, foolish, and unfit to lead, unlike himself of course.

The threat was handled by the Hunting Hero, Kizuna Kazayama, who was summoned to slay the Demon Dragon. After his defeat, the Demon Dragon's body was used for resources. His body unlocks the Demon Dragon weapon in the Holy Heroes, who all use it as their new default weapon due to its good stats, abilities, low-level requirement, and easy ability to use.

Volume 9
When in Glass' world, Naofumi unlocked the Demon Dragon Shield and had part of the Demon Dragon's core crystal merged with the Dragon Emperor shard from his world and integrated into his new Barbaro Armor. This linked the mind of the Demon Dragon to Gaelion's who was in the original shard. This allowed the Demon Dragon to sneak into the Shield.

During the battle with Kyo Ethnina, he offered Naofumi the chance to use All Sacrifice Aura against him, massively increasing the stats of Naofumi, Raphtalia, and Filo for a short period of time in exchange for a powerful curse that leaves the trio crippled for a month.

Volume 12
Later, when the new Baby Gaelion ate Naofumi's Dragon Emperor shard both the minds of the Demon Dragon and the old Gaelion went into Baby Gaelion's head along with Naofumi's rage from the Shield of Wrath. This caused baby Gaelion to go out of control. The connection through Dragon Emperor fragments caused Filo's exp to be drained into baby Gaelion's body. The new entity flew to old Gaelion's mountain cave near Mirso Village in Melromarc.

After being shaken by Wyndia's words, the Demon Dragon shoved both Gaelions' minds out and took control of the beast. He made his demands clear and his intentions to use both Filo and Naofumi as sources of power in his global conquest. The Demon Dragon could lock Naofumi out of the Shield of Wrath and could upgrade it freely to make himself more powerful. He possessed the Shield of Wrath's defensive might and Dark Burning S.

After being weakened by multiple Hengen Musou attacks, Baby Gaelion was able to escape with Filo. This caused the Demon Dragon to become the Wrath Dragon. When the Wrath Dragon was defeated, the Demon Dragon's mind retreated back into the Shield, saying it will stop for now.

Volume 18
After Naofumi returned to Glass's World in order to help his fellow Holy Hero, they found themselves overcome by the reincarnator's abilities to negate their buffs and the strength of Syne's sister, so in order to turn the situation around, Therese suggested resurrecting the Demon Dragon, a master of magic, to help them. Although many were opposed to the idea, the group decided to give it a try and if they failed they would have Kizuna kill him again. In this way, the Demon Dragon was resurrected using the cores that Naofumi had in his armor by inserting them into a Dragon Egg, restricted by an ofuda (hero) in order to make to make Kizuna its master. Also, listening to Naofumi’s experience, Kizuna decided to make female the gender of the egg.

Upon resurrection as a baby, the Demon Dragon showed little surprise by the decision of the heroes of asking her help and confirmed that no ofuda could slave a Dragon Emperor, allowing her to disobey them if she wanted to but she stated that she would end dying anyway if she had to fight the Hunter Hero in her weakened state, so in order to move on she offered a truce in which she would work with them to overcome the danger of the Waves and would refrain from taking actions against humans for 100 years.