There are portals connecting Aernas to Elyos, but they have been sealed after the events of the First Demon Wars. The people of the Holy Kingdom in Bermesiah serve a god that maintains and protects the gateway between the two worlds. However, as a result of Ashtaroth's actions, the barrier between the two worlds has become unstable and weakened, allowing portals connecting the worlds to be opened across Aernas.
In the beginning, the Creator had created deities, the ones who would be responsible for creation of the universe, and the demons, who would be responsible for destruction.
Because of their belligerence, instead of being together with deities in the physical world, the devildom, Elyos was created in order for the demons to reside. When they felt the necessity, the demons traversed through the dimensional portals to cause destruction in Aernas. When the demons are created in the beginning, ancient demons are made because of the mutation. They lived in the nook of Elyos, separated from the other demons.
Sometime before the founding of Kounat, the League of Demons initiated a surprise attack on the ancient demons, leading to the Ancient War where the ancient demon's hero, Duel Von Zec Avenger (Void) went berserk. He annihilated everyone in disregard of whether they were allies or enemies, and because of that the war was practically terminated.
Oz Von Max Linehart, a legendary magician who participated in the war on the demons' side, was almost killed by Duel and fled. He retreated to his hideout, and started to construct the magical sword that will rival with Duel's Eclipse, Grandark. After placing his final touches to the magical sword, Grandark, Oz started on “creature research”, to find a physical entity that will control Grandark in his stead. He investigated the old territory of the ancient demons in order to find the ancient demons’ core, an essential of creature creation.
Many years later, the demons of Elyos invaded Kounat, initiating the First Demon Wars (before the birth of Mari Ming Onette). In Elyos, unsatisfied by the destruction set by the Creator, the extremists who supported the indiscriminate demolition began to gain power. The conflict led to the birth of two factions within Elyos, the extremists and the moderates.
The leader of the extremists was a high ranking demon, Heitaros Cratsus, who led his demon army through the dimensional portals and destroyed countless stars, and who now set Aernas as his next target.
Because of Heitaros, a dimensional portal had opened in the eastern territory of Kounat in Archimedia, and countless demons started to infiltrate through this. Their first order was to destroy the powerful magic civilization of the deities, and they charged into the kingdom of Kounat. After hearing the news about the extremist invasion, the Burning Canyon clan sent Dio to Aernas as a missionary.
After being informed of the invasion, the three Goddesses and the King of Kounat led Kounat's regular army to the Artione Field, which is the gateway to Kounat and engaged in battle against the demon army. During this fierce war, many casualties were brought about.
After a hard, drawn out fight, the Kounat army initiated the Aernas’ Hammer, the saisyu heiki (final ordinance) of Kounat, which allows the power of the Gods to be in use through the divine power repertory device reconstructed into a weapon, albeit unstable.
Heitaros was critically injured, and fled back to Elyos through the dimensional portal. The first wave of the demon army was nearly decimated, and after losing their leader, the soldiers scattered to the whole regions of the continent.
However, after losing almost all of their power due to the war against Heitaros, the three deities sealed the dimensional portal and returned to their world as well. In the process, Dio was not able to return to Elyos, and was trapped in Aernas. Demons who fled spread out to the various regions of the Aernas, and continued to destroy that world by mutating the local life forms into monsters.
The prosperous era under the Gods had passed, and now the era of chaos due to the fear of the monsters’ invasion had started.
Trivia is the threshold to the portal leading to Aernas. Located at the end of Elyos, Trivia is a barren region at the edge of a massive floating island surrounded by mountains and several island clusters. All Asmodians wishing to enter Aernas must first pass through this region. Trivia is guarded from intruders by black holes that suck and destroy souls.
The demons inhabiting Elyos are known as the Asmodians, and a large majority of the demons in Grand Chase come from this race. The Asmodians were originally created to destroy other creations and thus maintain the balance of the worlds.
Within Elyos, the Asmodians are separated into tribes, with many of these tribes forming alliances with others sharing similar views and opinions. There are two major groups seperating the Asmodians from each other, one group that prefers to follow their original purpose of destruction and another group who are against it and just want to live in peace with all the rest.
It is this clashing of perspectives that led to the First Demon Wars when the kingdom of Kounat became far too powerful, attracting the attention of Asmodians who thought of the kingdom as a threat. The more aggressive tribes such as the Terres were enthusiastic about the demonic extermination of humans, while other, more pacifist tribes such as the Burning Canyon tribe and the Crimson River tribe, opposed to this idea and sided with the humans. The conflict led to a violent war, where magic, technology and the dark forces crossed the battlefield.
Amongst the demons encountered during gameplay, Drawl and Veron who are encountered in the Relics of Kounat are also Asmodians. Possibly, Quoronnos who is fought in Zeruel is one as well, though likely to be one of the more beastial kinds.
The main difference between the demons of Elyos and the demons of the Underworld, the Haros, is the presence of horns in the Asmodians. Some Asmodians also have wings and tails that they can summon or retract at will. The Haros have a lighter skin tone and lack the horns, in addition to possessing shorter ears. The Asmodians know of the Haros, and even they fear the bounty hunters as evidenced by Dio, who with his immense powers was overwhelmed by Rufus's speed and chose to flee from him when the Haros targeted Ley in the Wizard's Labyrinth.
- The name "Elyos" is likely a play on "Elrios", the name of the setting in Elsword.
- Elyos, Asmodians, and their history are only stated in the Naver Blog; they are never said in-game.