Ysmault is located somewhere in Sector 2814 and, at one time was, the throne-world of the Empire of Tears, a galactic empire ruled by demons. The Empire was battled by the ancient Maltusians, precursors of the Guardians of the Universe, in their efforts to contain the wild magic of the universe. After the Empire's defeat, all its members were imprisoned on Ysmault, and access to the planet was restricted by the Guardians.
Abin Sur, while a green lantern, was forced to violate orders to save the passengers of a crashed spacecraft. While there, he made the mistake of speaking to Qull of the Five Inversions, who set him on the path to his eventual death by answering a question about Sur's future. Sur later would demand more information from another Inversion, Atrocitus, who held crucial information divined through blood rituals related to the Blackest Night.
Later, Sur took Atrocitus to Earth; Sur perished in this mission and it was Sinestro and Hal Jordan who brought back Atrocitus to Ysmault. Atrocitus, at one point, would brutally kill the remainder of the Five Inversions and use their blood to power a massive Red Lantern Power Battery, and forging red rings out of the crystallized blood, forming the start of the Red Lantern Corps. Ysmault has since served as the Corps' home-world.
Atrocitus conducted experiments upon the Red Lantern home-world of Ysmault in an area known as the abominable zone which was a complex built from remains of stranded space travelers. Here Atrocitus conducted his experiments to fill the numbers of his corps. The creations ultimately failed him as he saw them as grotesque and insane lifeforms. These lifeforms were slaughtered and buried beneath the soils of the abominable zone, and over time the corpses fed the grounds and yielded plant growth to this barren planet.
Here Atrocitus returned to confront Krona and was meet by Abysmus one of the failed experiments who now seeks vengeance for his abandonment.