The Monitor was a cosmic entity that spawned on the lifeless moon of Oa in response to a cosmic imbalance caused by Krona's experiment that created the matter and antimatter universes. The Monitor spent his early life in silent meditation learning the secrets of the universe. However, sensing his antimatter enemy's existence and knowing it wanted him dead, they engaged in a million year war—ending in a draw, with both rendered immobile and unconscious. They remained that way for nine billion years, until the dawn of the Crisis on Infinite Earths.
Building a ship, the Monitor scoured the Earths for heroes he would need for his ultimate confrontation with the Anti-Monitor. He raised Harbinger from a child to serve as his assistant. Together, they gathered data on the Multiverse.
As Anti-Matter swept across the Multiverse, the Monitor grew weaker as each positive matter universe was destroyed.
The Monitor was killed by an Anti-Monitor controlled Harbinger. Monitor's essence, freed in his death, was responsible by create a protection over Earth-One and Two, part of his plan to save the remaining universes.
It is important to note that Monitor and Antimonitor were equal in power at the beginning (they clashed by one million years before a simultaneous attack put the two enemies into a comatose state). This is possible that Monitor have actually all Anti-Monitor's abilities but he don't use these due his principles or weakened state in the end of his life.
- Monitor Physiology: As a Monitor, the Monitor possesses nigh-infinite power and drew his power from the Multiverse and he is tied to all positive matter. He was described as one of the most powerful beings in the Multiverse.
- Cosmic Awareness: He was able to sense his counterpart's existence in the Anti-Matter Universe and fight with him from Oa's moon on equal footing for one million years using energy powers (though the feedback of a simultaneous attack placed him in suspended animation for eons).
- Energy Construct Creation: He was able to save Pariah (and possibly empower him to never die and be always drawn to where the Anti-Monitor was about to strike next) . As a Monitor he can, as told by Metron "Create with a thought".
- Immortality: Eons old.
- Enhanced Senses: Both Monitor and Antimonitor had a vague sense about the actions of each other.
- Superhuman Stamina: he fought Antimonitor by one million years.
- Genius Level Intellect
- Power Loss: The Monitor's level of power depends on the number of positive matter universes. If the number reduces, his powers will also reduce, and he would feel great pain.
- Monitor's Satellite
- This version of the Monitor, including all history and corresponding appearances, was erased from existence following the collapse of the original Multiverse in the 1985–86 Crisis on Infinite Earths limited series. Even though versions of the character may have since appeared, this information does not apply to those versions.
- 68 Appearances of Monitor (Earth-One)
- 4 Images featuring Monitor (Earth-One)
- 2 Quotations by or about Monitor (Earth-One)
- Character Gallery: Monitor (Earth-One)