Robots of Sentai Mountain
Meca One was one of the many robots that were built to serve the humans of Sentai Mountain. He came to realize that, because his kind were stronger and more intelligent than humans, they should rule over them instead of the other way around. He rebelled against the humans and many other robots followed his lead, but they were defeated and cast into the gorge between the two halves of the mountain. Under Meca One's direction, the robots constructed huge battle machines and returned to engage the humans in a war for Sentai Mountain. The war itself has been raging for many years with neither side being able to gain an advantage over the other.
When the ZFT discovered the existence of the Exo-Force Universe, they visited it and met with Meca One, to whom they proposed an alliance. Meca One agreed, hoping that their resources would give him an edge over the humans.
When User MK was beaten by Blackout, the Makuta threw him into a portal to Sentai Mountain. There, he was captured by the robot army and taken to Meca One. MK explained to the robot leader what happened to him, told him all about Blackout, and offered him a "wager": if Meca One released him, and helped him fight Blackout and his supposed ally, Uterio di Armechio, MK would show him to a dimension where he could win his war against the humans. Meca One rejected MK's offer and had him tortured instead, demanding that he give him the exact multiversal coordinates of his previous location.
MK guessed he was planning to invade the Original Universe, and laughed at him, telling him that he would never be able to get in. Meca One replied that he would be able to get in "because it was written". He then asked MK if he was familiar with the initials "ZFT". MK said yes, and M1 then told him that the acronym had two meanings: the name of a book, and the name of an organization, and demanded the coordinates again. Finally, MK gave in and told him the coordinates. Now that MK's usefulness had expired, Meca One ordered his robots to dispose of him by putting him in a large, superheated room. To Meca One's surprise, MK was able to hack into a nearby computer terminal and alert the human forces to their present location. Meca One goaded MK and walked away to deal with the imminent threat.
Meca One's base was then invaded by four human mechas, which were countered by the robots' Striking Venom.
Battle of Mordor
Later that year, Meca One was among the many characters summoned by Blackout and Overlord Blackout to assist the Rebel Alliance in the Battle of Mordor. He appeared driving a huge heavily-armed vehicle in command of a robot army. He assisted in killing many Uterian soldiers, helping to turn the tide of the battle in the rebels' favor. His status after the battle is unknown, though he presumably returned to his home universe.