SPOILER WARNING: This article contains major spoilers for "Mercy," the latest episode of Krypton.
Krypton just introduced two major pieces of Superman mythology: the Black Mercy and Fort Rozz.
The Black Mercy originally debuted in 1985's Superman Annual #11, which featured a self-contained story called "For the Man Who Has Everything" by Alan Moore and Dave Gibbons. In the now-iconic story, the Man of Steel falls victim to the Black Mercy thanks to a villain called Mongul. As Mongul explains to Batman, Robin and Wonder Woman, the Black Mercy traps its victim in a fantasy world that gives them their heart's desire.
Krypton's Black Mercy works the same way. "It's called a Black Mercy. It's a parasitic plant from another world," General Zod explained to his scientist Lis-Ser. "I discovered it within Val-El's fortress. It creates an entire alternate reality in the mind of its host."
In this case, the Black Mercy's host was his mother Lyta-Zod. Zod employed it to keep her sedated and unchanged long enough for him to accomplish his goal of universe-wide colonization. The parasite caused her to envision a world where she was able to bind with Seg-El with the full support of her mother Jayna and friends.
However, Zod hoped to use its toxin to subjugate Doomsday and turn the creature into a weapon. In the process of extracting the toxin, Lis-Ser warned it could negate the Black Mercy's effect on Lyta. "The Black Mercy is having a negative reaction to the extraction," she explained. "I'm concerned that the Black Mercy's negative reaction to the extraction could cause Lyta's fantasy to collapse entirely." Nevertheless, Zod urged her to proceed.
"The half-life of this toxin appears to be limitless. Once exposed to the Black Mercy, a person could remain under its influence forever," she added.
Zod also revealed how to escape the Black Mercy's clutches. "Amidst my travels in the future, I encountered the Black Mercy. I learned the only way to break its hold is to reject the fantasy it creates, but there are few with the awareness to see beyond the illusion and even fewer with the will to give it up," he said.
While the Black Mercy eventually suffered from the extraction of its toxin, that toxin ended up performing exactly as Zod hoped. "I'm confident this dosage will allow Doomsday to remain cognizant, yet pliable," Lis-Ser told Zod. "He'll be in a suggestive state, but won't succumb to the toxin's psychoactive effects."
In addition to the Black Mercy, Krypton introduced Fort Rozz in "Mercy." The Kryptonian military installation originated in E. Nelson Bridwell and Curt Swan's The Krypton Chronicles #2 in 1981. Over the years, Fort Rozz became a high security prison instead, where convicts were held until they were banished to the Phantom Zone. In Krypton, Fort Rozz serves as a reconditioning facility as well as a military complex.
In "Mercy," Seg planned to infiltrated it with Jayna, Dev-Em and Nyssa to stop General Zod's fleet of interstellar ships. Once Dev and Jayne reunited with Seg and Nyssa at Val-El's Fortress, the two former Sagitari laid out their plans.
"Zod has announced the first fleet of his interstellar ships is complete," Dev said.
"We closely monitored all Sagitari comm signals until we got the order to prepare for launch," Jayna added. "For Wegthor."
"We believe Zod is planning on launching a final assault on the resistance," Dev explained. "Send them everything he has and make sure no one is left standing."
"We can't warn them about the launch. We're going to have to stop it," Seg insisted.
"The only way to stop Zod's fleet is by destroying it," Dev shot back. He revealed that they intended to infiltrate Fort Rozz in order to carry out their plans.
"So, breaking into Fort Rozz," Seg said cavalierly, despite the odds. "Gotta get easier with practice, right?"
"On the eve of a launch, every Sagitari will be on duty," Dev replied. "They'll have new security codes. New patrol routes in every sector. If we want to get inside, we'll have to think of a way Zod hasn't."
"I know a way," Seg admitted. "Back before we were all friends, Kem and I used to -- shall we say -- liberate various good from the Guilds and redistribute them to the rankless. We used tunnels that ran close to Fort Rozz... Stupidly close. 100 feet to the north."
"Right beneath the spot where Zod built his shipyard," Dev pointed out.
"There's an armory that only the Primus is informed of. It's heavily defended by defense protocols, so it has fewer Sagitari protecting it, but I know how to disengage its security measures," Jayna revealed. "We just need to get there."
Their plan went sideways when Seg and Nyssa were captured by the Sagitari. Jayna and Dev switched their focus to a rescue. This led them to reunite with Lyta, then they successfully freed Seg and Nyssa. However, their bold actions encouraged Zod to move up his timetable and usher in the utter destruction of Wegthor.
Airing Wednesdays at 10 pm ET/PT on Syfy, Krypton stars Cameron Cuffe as Seg-El, Shaun Sipos as Adam Strange, Georgina Campbell as Lyta-Zod, Elliot Cowan as Daron-Vex, Ann Ogbomo as Jayna-Zod, Rasmus Hardiker as Kem, Wallis Day as Nyssa-Vex, Aaron Pierre as Dev-Em, Ian McElhinney as Val-El and Blake Ritson as Brainiac.