The Monitors are a multiversal race charged with the protection of the Multiverse.
During the first multiverse, there were only two, the Monitor and the Anti-Monitor, who oversaw the multiverse and the anti-matter universe respectively. Both were killed during the events of Crisis on Infinite Earths.
After the creation of the new multiverse, a new race of 52 different Monitors is seen to be active trying to protect the multiverse from corruption as a community. Each monitor is assigned to its own world, and they all vary at least slightly in appearance. A version of the Anti-Monitor is also seen to be active helping the Sinestro Corps on Qward. Although they are seen again, the Monitors play their next largest roles in Countdown.
In the end, the revised origin of the Monitors took this form: in the beginning, a gigantic, limitless, vast intelligence named Monitor but referred to in places as "Overmonitor" or "Overvoid", discovered the Bleed and the Multiverse within, a 'flaw' at its heart. Disturbed, it sent out a probe in a similar form to that of the original "Monitor" from Crisis on Infinite Earths that fed back the chaos of every story of the Infinite Earths all at once; overwhelmed by the very idea of a "story," the Monitor recalled the probe and sealed off the Bleed by creating the Multiverse Machine (or "Orrery of Worlds"), but his contemplation of the workings of the Machine (doubtless combined with the established fact that the Monitor was linked to all positive matter) resulted in the generation of the World of Nil, populated by powerful vampiric beings with a vast and epic history, living and continuously evolving manifestations of the Monitor's thoughts, who see themselves as "descendants" of the Monitor himself.
Many years later, it was eventually revealed that the Monitor race was created by The Presence in order to restrain and regulate the new Multiverse that was born as a result of the Infinite Crisis so that it could slow down the awakening of its' ancient rival aka the Great Darkness albeit the Monitors' best attempts had done little in stopping the primordial darkness' awakening.
Main article: Countdown
Controversy emerges for the Monitors when two with radically opposing viewpoints argue about how the multiverse should be maintained, the chief concern being the presence of "Multiversal Anomalies" (people who have hopped from world to world). Monitor Solomon of Earth-8 believes such disturbances should be immediately eradicated, and goes as far as to hunt down and kill Duela Dent. Despite his violence and zeal, he manages to convert almost all of the Monitors to his way of thinking. However, New Earth's monitor, Bob, believes a much more peaceful approach should be taken, and establishes the Challengers of the Unknown, a group made of anomalies to help him track down Ray Palmer who he believes is the only man capable of averting the upcoming Great Disaster.
The violent actions of the majority of the Monitors, including the genocide of the Forerunners, attracted the ire of Monarch, who believed them to be tyrants. Using the Bleed as his headquarters, he gathered an Army from all over the multiverse to challenge and destroy them, almost suceeding, culminating in the destruction of Earth-51. Monarch's whereabouts are currently unknown, all of the Monitors survived the Monarch War, except for Bob who was specifically killed by Solomon as Solomon attempted to directly absorb Bob and amass Bob's power for himself.
Although the Monitors were originally very close (some were specifically female while the bulk were male gendered), they have been changed drastically developing individual personalities and choosing through mutual best interest rather than a resulting singular mental/intellectual focus as shown when their base individual realities were drastically changed by Mister Mind during the end portion of the interdimensional 52 event. Thus the Monitors have also changed to reflect them, and have since been becoming more and more individual and acting in mannerisms that would be considered individual greed of their particular reality and at times of their own individual person which resulted in the attack and removal of Solomon from their collective assembly.
Recognizing that the Monitors are more or less now completely individuals and thus increasingly dangerous to the stability of other individual realities, the Monitor of the destroyed Earth-51 Nix Uotan has recently put together a team to monitor the Monitors. The Monitor Guardian team consists of Ray Palmer, Donna Troy, Kyle Rayner and Forager.
Main article: Final Crisis
The Monitors were eliminated as a superpowered species as part of Nix Uotan's plan to safeguard the 52 individual realities from the Monitors' own vampiric nature as well as the plan instigated by Darkseid to reformat the universe to his own designs. Nix was reborn as a human teenager on Earth-0 with some rememberance of his existence as a Monitor.
It was confirmed that only Nix Uotan himself survived the extinction of his race. Thus, only himself and the Anti-Monitor remain as representatives of this set of beings, though technically the Anti-Monitor is not part of their race.
Powers and Abilities
- Enhanced Intellect: Monitors possess an infinite knowledge about the secrets of the multiverse.
- Reality Alteration
Habitat: individual habitats as well as collective space station in the Bleed
Population: Only 1 of the original 52 remain. Nix Uotan, who propagated the destruction of the Monitor race during the Final Crisis but was spared their fate, is the last of the Monitors, and defends the Multiverse from immense threats.
- This note does not include the current being known as the Anti-Monitor, who, like these Monitors, may now also be reflective of multiple antimatter realities that have been shown to exist. At present, there is only one revealed Anti-Monitor.
- Pre-Crisis Multiverse: The Monitor
- Anti-Matter Universe: Anti-Monitor
- Earth-0/New Earth: Bob killed by Solomon 
- Earth-6: Weeja Dell
- Earth-8: Solomon
- Earth-43: Zillo Valla
- Earth-51: Nix Uotan
- Unspecified source Earth: Doctrine primary female Monitor