Behold the power of a god!
—Overlord, Etrian Odyssey II: Heroes of Lagaard
The Overlord is the master of the Yggdrasil Labyrinth. He is a god-like being that resides the Heavenly Keep and holds the power of the Holy Grail (Grail of Kings in the remake), a concoction that is said to be able to give eternal life to humans. He is responsible for the creation of most of the monstrosities that resides the labyrinth, which are result of his failed experiments on immortality.
The Overlord, like Visil, is a scientist that managed to survive the apocalypse. He, along with other people, managed to live on by holing themselves for ages on a flying fortress, the Heavenly Keep. At some point, the Overlord started running experiments on humans using an artifact known as the Holy Grail, trying to achieve eternal life. His experiments where a failure though, transforming the subjects into mindless monsters.
Realizing that his own mortality was getting in the way of his research, which would take several lifespans, he decides to upload his mind to an immortal, mechanical body so he could continue with his research for all eternity, if needed.
A long time after these events, the chaos caused by the great calamity that struck the world began to cease, allowing people to descend from the castle, braving the dangerous new lands and, once again, establishing society on land.
Hundreds of years have passed, and people have forgotten all about the flying castle their kind once called home, its knowledge being restrict to a select few. However, when the Grand Duchy of Lagaard fell terminally ill, the people that knew of the legends decided to, once again, seek the flying castle as the nobles of the city believed the Holy Grail would be able to cure their dear leader. In order to reach the Heavenly Keep once again, however, they had to cross the dangerous Yggdrasil Labyrinth, a humongous tree that at some forgotten point in time after the calamity mysteriously rose endlessly towards the sky.
Many have died in the dangerous journey, and the Overlord saw that as an opportunity to secure test subjects for his research. He made a contract with the birdfolk, a tribe of intelligent humanoid creatures living in the highest branches of Yggdrasil, the Petal Bridge. Posing as a god (thus his title of Overlord), he ordered the birdfolk to bring corpses of dead adventurers to him, acting like "angels" bringing souls to their god never to know their master true intentions. And thus this cycle continued, until the Heroes of Lagaard came to the land, finally posing a true challenge to the Overlord, and his failed creations.
Etrian Odyssey 2 Untold Edit
While the Overlord's role remains the same in the game's remake, a few more details on his backstory are given in the story mode.
It is revealed that, in fact, the Overlord was the original creator of the Heavenly Keep. He was a member of the Yggdrasil Project, and the original goal of his research was to give mankind means to fight and defeat the Yggdrasil Cores. He was then aided by an engineer of the keep, who helped to further his researches. However, when mankind chose to return to land, she decided to return along with them, eventually becoming the Black Guardian and creating a ritual to seal one of the fearsome cores deep inside Ginnungagap.
When he found of the existence of the Knight of Fafnir, fruit of his old friend's research, the Overlord desired to take the knight's power for himself, by killing the protagonist and infusing himself with his powers, taking into himself the responsibility of killing the core. However, the protagonist and his party, defeat the Overlord in the end; thus he decides to use his last breath to grant them the Grail of Kings and its powers, so that they finally can make a stand against the core (realizing that the Fafnir Knight and his party would have an easier time killing the Yggdrasil Core than he would).
Etrian Odyssey 2 Untold also suggests that the Overlord may have created the birdfolk, although this is never explored much in the game's story, so it is currently left ambiguous whenever that's true or not, or what methods he may have used to do so.
- "Behold... the prime fruits of my research. The Juggernaut born from limitless power!" (When introducing the protagonist's guild to the 'Black Beast')
- "Show me what her research has wrough! The power that surpasses human potential! Exert your might to its fullest!" (When the guild was about to fight the Juggernaut)
- The Overlord is never referred to by his real name, so it is unknown so far.
- The Overlord very much resembles a biomechanical version of the Elder Dragon, and, fittingly, has has a number of similar attacks. It is heavily implied that the Overlord's current form was based on research into the Dragons, which may very well explain his true form.
- Its implied that many monsters, including some bosses (Chimaera, Hellion Scylla, Colossus, Ur-child and Ur-Devil) are, in fact, failed experiments on humans that resulted in those creatures.
- The game over the player gets upon agreeing the Overlord offer, is, most probably, because his research isn't complete yet. This means that the characters are either killed, or turned into monsters like the other test subjects.
- The Overlord, like the other final bosses of the series, isn't intrinsically evil, but does not follow a moral code. Whatever nobility his goals may have are vastly eclipsed by his capacity for doing whatever he deems necessary to those he experiments upon.
- The Overlord may be more spiritual and may have greater spiritual power than many of his colleagues (who are scientists like him), possibly explained by the fact that, after his death (in both Classic and Story Mode), his body dissipated into motes of light, and in the original EO2, after defeating him in his first phase, his body is said to crumble, but he still speaks to the players and his body is seen once again (in his first form before entering his second one), seemingly unscathed.