Solomon was the Monitor native to the universe known as Earth-8. Solomon was the first of the Monitors who emerged in the creation of the 52 Multiverse who developed individuality from the almost hive like mindset of the other Monitors and self-adopted the name of Solomon as an indication of his great wisdom to the other Monitors.
It is unrevealed when Solomon decided to go against his brother and sister Monitors. But he was the first to decide an agressive plan of universal containment by finding and eliminating any and all known extra-dimensional travellers. Solomon was able to convince most of his brethen to support him in this manner or at least allow him a free hand and not be directly opposed to his plan including the seemingly opposing Bob of New Earth. Bob later rejected Solomon's extreme attitude to "dimension hoppers" except in cases where these dimension hoppers posed an open threat to the multiverse such as the Monarch.
Solomon's plan of individual universal containment was ultimately revealed not to be a protection device for each individual reality, but a long-term self advancement plan similar to the Anti-Monitor. His plan was designed to increase his own personal power and allow him to become more powerful than any other individual Monitors referred to the others as Prime Monitor which one of the female Monitors states is a myth. When Bob confronted Solomon on the matter, Solomon revealed this plan and attempted to directly absorb Bob's powers into himself. Unable to take Bob's powers for himself, Solomon killed Bob.
While the other Monitors were repulsed that Solomon would kill one of their own, they supported Solomon in the recent Monarch War. After the war, fearing that Solomon may resume his attempt to take their powers for his own and control them, the other Monitors banished Solomon from their ranks for his attempt at domination over them. It was then revealed that Solomon had been playing against Darkseid this entire time, both striving for control of the Multiverse.
Solomon is planning to resume his attempt to control the other Monitors but is merely maintaining his vigil of the Earth-8 dimension for the time being. When the young Monitor Nix Uotan was banished for his failure at Earth 51, Solomon was the only one who rejoiced, glad that he now stood unoposed.