What exactly is a Black Mercy? Zod’s description of the plant in tonight’s episode is actually pretty accurate. A Black Mercy is, in fact, a parasitic plant that taps into the pleasure centers of a person’s brain, creating a dream of the person’s perfect life while also keeping the victim completely paralyzed. The plant then feeds on the psychic energy produced by the victim as they interact with their dream.
The Black Mercy first appeared in the classic Superman story “For the Man Who Has Everything” from Superman Annual #11 from 1985 by Alan Moore and artist Dave Gibbons. In that story, Batman, Robin, and Wonder Woman visit the Fortress of Solitude with gifts for Superman on his birthday. However they find the hero catatonic, the Black Mercy on his chest with tendrils wrapped around his body. That’s when Mongul appears and explains what the plant does and reveals that, in the plant-created coma, Superman is living the dream of a normal life on Krypton
However, while the Black Mercy sounds like something that might be enjoyable — who wouldn’t want to be forever in their perfect fantasy? — it’s not quite as nice as it sounds. In the story, Superman’s fantasy life takes a dark turn and that’s something we see in tonight’s Krypton as well. However, that actually isn’t necessarily a bad thing as, in comics when the person trapped in the fantasy realize it is just that, a fantasy, the Black Mercy slowly begins to lose its grip making it easier for the plant to be detached and its victim freed.
Krypton airs Wednesdays at 10/9c on SYFY.