Red Demons

The Red Demon was part of the Demon Clan, who (probably wanting the water of the Fountain of Youth) burned the Fairy King's Forest. After it fatally wounded both Ban and Elaine, the former drank the water and then quickly defeated the demon with his new-found immortality.

Appearance
It was a very huge and fat creature, with a clown-like face, sharp claws & teeth. Its two horns had rings that were alternatively colored black and white. Its blood vessels were visible on the neck.

Personality
It was a wild and vicious beast, going on rampages with reckless abandon to achieve its goals.

History
This Red Demon was a part of the Demon Clan, which was sealed for eternity after losing to the Goddess Clan allied with the Humans, Giant Clan and Fairy Clan in an ancient war. However, it somehow escaped the seal.

Bandit Ban
Just as Ban offered to find Elaine's brother, the Red Demon suddenly appeared, probably to steal the Fountain of Youth, and started burning the Fairy King's Forest with its purgatory fire. Ban, immediately instructing Elaine to take the cup of the fountain and escape, began attacking it and successfully removed its heart. However, it did not die, since demons possess more than one heart, and then fatally wounded both Elaine and Ban with its claws. After Elaine made Ban drink the Fountain of Youth, he becoming immortal, quickly and angrily defeated the demon.

Sometime after it was killed by Ban, its corpse was found by some knights who were sent to investigate the Fairy King's Forest's destruction, including Hendriksen, who also discovered a power enhancing quality of the demon's blood, and that its blood could transform compatible living beings and draw out immense power after witnessing crows mutated after they ate its flesh. This quality of its blood has been used by Hendriksen to secretly increase the abilities of many ordinary Holy Knight apprentices, many of whom were considered as failures. The apprentices were called the "New Generation" with the kingdom unaware of their new abilities' origin. Hendriksen also experimented on himself as well, resulting the obtaining of Demon powers and Hellblaze.

Byzel Fight Festival arc
Twigo and Jericho are brought to the cave, where the Red Demon's corpse is hidden by Guila. After receiving explanations about the qualities of its blood, the two decide to drink it due to their desires for greater strength. Twigo, however, explodes due to being incompatible; Jericho remains fine and survives after ingestion.

Kingdom Infiltration arc
As Great Holy Knight Dreyfus leads a strike group of Holy Knights (Gilthunder, Hauser, Guila and Jericho) into Merlin's old castle, Helbram expressed worries of what would happen if Dreyfus find the Red Demon's corpse beneath the castle before encountering Diane underground.

Later, when the five of the Seven Deadly Sins battle Hendriksen at the ruins of Merlin's old castle, Ban discovers the corpse after being sent flying into the wall by the Great Holy Knight. Recovered, Ban questioned the Druid's acquisition of the corpse and then assaulted Hendriksen in full force, that sent him flying into the wall. The wall collapsed to reveal the chained demon's corpse with the Sins' shock and Hendriksen laughing in confidence. Hendriksen reveals how he came by that corpse and used it to make countless experiments on the Old and New Generations and himself, boasting of the vast powers he had gained before attacking the Sins again with Ban taking the blow and revealed to the Great Holy Knight that he was the one who killed it 20 years ago before pummeling him. After Ban smashed Hendriksen far deep underground, the Fox's Sin of Greed destroyed the demon's corpse with his nun-chunks.

Abilities/Equipment
Being a demon, it had all of the species' standard abilities and features while it was alive, which included possessing multiple hearts and the ability to release purgatory fire (the only fire that can burn the Fairy King's Forest) from its mouth. It also had great physical strength and speed, which it displays when it fatally wounds both Ban and Elaine before they could realize what had happened. Its blood, when drunk, has the capability to transform and enhance the powers of compatible living beings; incompatible creatures, however, explode after drinking it.

The demon could form a dark matter like wing, which it used to fly over the Fairy King's Tree.