They were originally a human species called the Femushinmu until their civilization was invaded by the Helheim Forest. According to DJ Sagara, a few of the former humans that resided in Helheim gained transcendent power, thus becoming the Overlords of Helheim and exterminating the remaining weaker members of their species.
Overlord Inves are able to control all of Helheim to their whim, meaning that they can command flora and fauna to do what they want. Despite this, they are still at the whim of the Helheim Forest itself and its true ruler.
While referring to themselves as Humans, the Overlords call humans "apes". It should be noted that the Overlord Inves are notoriously lazy when compared to other rulers, letting Helheim slowly consume worlds while they sit around in the shadows. However, when provoked, they will not hesitate to attack and throw a lot of power into their attacks. By the current day when the series begins, there seems to be only 6 Overlords left, the rest having presumably perished in the years following the fall of the Femushinmu civilization.
The Overlords were once a race of human-like aliens known as the Femushinmu, whose planet was invaded by the Helheim Forest. Led by Rosyuo, several of the Femushinmu embraced the power Helheim bestowed upon them and used it to exterminate the weaker members of their race, leaving themselves as the only survivors of their civilization. From then on, the Overlords ruled over Helheim Forest, sitting back as it would go on to consume more and more worlds.
Eventually, when the Helheim Forest reached Earth, the Overlords would come into contact with humanity after Demushu encountered Kamen Rider Baron. After Redyue provoked the humans into launching missiles at Helheim, Rosyuo was motivated to fully declare war on humanity and speed up Helheim's rapid encroach on Earth.
Though the Overlords were later wiped out by the Kamen Riders, Kaito Kumon would eventually become a new Overlord Inves by eating a Helheim fruit and maintaining his mental state through sheer willpower, becoming Lord Baron.
- Three out of five of the Over Lord Inves are equivalent to three out of four of the main Armored Riders and the three Phantoms from the previous series, Kamen Rider Wizard. Additionally, the Heroes Kouta Kazuraba (Blue Armored Rider), Lapis (Navy Over Lord) and Haruto Souma are a hope bringing warriors who has blue and shining color themed forms.
- Rosyuo (Chalk Over Lord), Takatora Kureshima (White Armored Rider) & Carbuncle Phantom/Wiseman: Three of them are leaders to their groups, and are betrayed by their subordinates. Rosyuo saved Takatora when he was lost in the forest. Also, Rosyuo's desire to revive the Over Lord Queen was similar to Wiseman/Fueki trying to revive his daughter. Luckily, after discovering the Child care is an experimental place for children to work for Yggdrasill in he future, forever, by Takatora and Mitsuzane's father, Amagi Kureshima, Takatora later reminded what Kouta said if he shows mercy towards the victim like Hase was, think about restarting to find a way to save humanity in finding a cure without any sacrifices like Hase and Yuya before.
- Demushu (Crimson Over Lord), Kaito Kumon (Red Armored Rider) & Phoenix: all three of them are power seekers and dies afterwards. Demushu is the first Over Lord Inves encountered by Kaito and he considers Kaito as his archenemy. Also, Demushu and Phoenix were rebellious towards their leaders and grew stronger in every battle.
- Redyue (Emerald Over Lord), Mitsuzane Kureshima (Green Armored Rider) & Gremlin: three of them are conspirators trying to overthrow their superiors. Mitsuzane busted Redyue's trap when she led them to the forbidden fruit. Also Redyue's playful and wise but destructive nature reflects Gremlin. In the end, Mitsuzane, whose being misguided by Yggdrasill's influence (particularly by Ryoma and Sid, and become just like his and Takatora's father, Amagi), realized he's been repeating a same mistake like his father was, then his brother when he was manipulated by Ryoma, such having Mai falls into a wrong hand Mitsuzane had been allied with many times.
- Phonetically, the Japanese kana for Over Lord can also be interpreted as "overload" and ties in with the Over Lords such as Demushu and Redyue, both possess overwhelmingly great power and both view humanity as toys for their own entertainment. Along this, the Over Lord Rosyuo views that his civilization was destroyed not due to the forest, but his civilization's own incompetence for viewing that only the strong should be allowed to live.
- The Over Lord are similar to the embodiment of some Lantern Corps from DC Comics. Green (Redyue and Mitsuzane) on the other hand is much opposite and became similar to Yellow Lantern/Sinestro Corps, until Mitsuzane's will becomes much more similar to the Green Lantern Corps in the end until onwards.