Black Mercy is a plant that creates a dream of a person's perfect life. They are harvested by Mongul. They tap into the pleasure centers of a person's brain. They have been seen to be used on Hal Jordan, Oliver Queen, Clark Kent, Bruce Wayne, and even the farmer himself Mongul. When someone discovers this reality is fake (they notice something wrong), or in other words they know their lives aren't this perfect, the Black Mercy will slowly lose its grip on its host, making it easy for it to detach itself from the host.
Superman: His father Jor-El's prediction was proven untrue. He is married to a composite of Lois Lane and Lana Lang and has two children. In the midst of this, Krypton is going into politcal upheaval. His cousin (who would be almost 16 years older than him now) is attacked by anti-Phantom Zone protesters.
Batman: In this dream young Bruce's parents' murder is foiled. He grows up and has a wife, Kathy Kane, and a daughter.
Green Lantern: Hal's father never died nor did his mother. Coast City was never destroyed. Sinestro never turned evil, and is his mentor and friend. They show the Green Lantern Corps fighting an unknown man possessed by Parallax. His family is together happy and he is dating his high school sweetheart Jen.
Green Arrow: Ollie is married to Sandra Hawke and has a great relationship with his son Conner. He has at least three kids. His son Connor Hawke was Speedy or the equavilant of it. His identity is publicly known.
Unknown: He is Superman
Unknown: A family man
Unknown: Won the Lottery
The worlds are temporary and people always break free. Either the plants lose their grip, or the people under its thrall may realize it isn't their lives or life isn't this perfect. It is possible it doesn't work because desires are empty.
- The Black Mercy plant appears in the Justice League Unlimited episode "For The Man Who Has Everything", which is based on the Superman Annual volume 1 story of the same name.
Links and References