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Arrowverse Wiki

"That was one messed up daffodil."
Maxwell Lord regarding the Black Mercy[src]

Black Mercy is an alien parasite that makes its host dream of their perfect fantasy world while it feeds off of them. It appears to be exceedingly rare, since J'onn, who is usually knowledgeable of worlds and beings beyond the solar system, knew nothing of it when one latched itself upon Kara.


It was used by Non to subdue Supergirl in order to proceed with the Kryptonians' plans uninterrupted. It attacked Kara in her apartment. When Alex Danvers attempted to remove it by force it almost killed Kara. When she successfully freed Kara from the Black Mercy-induced fantasy, the creature detached from Kara and shriveled up.[1]

When Lillian Luthor took her daughter Lena to Lex's secret vault, there was a Black Mercy amongst the cache of anti-alien weapons.[2]

Powers and abilities


  • Dream imprisonment: The Black Mercy can attach to another living being trapping them in their perfect fantasy life in a comatose state. It cannot be physically removed without killing the host, even if the host is Kryptonian. Instead, the host must reject their fantasy themselves.[1]
  • Super strength: Despite its size, the Black Mercy is able to effortlessly overpower and subdue seemingly any lifeform, even one as physically powerful as a Kryptonian, after tackling them. In fact, the creature is able to kill a Kryptonian, either using its thorns or the amount of pressure it can press, but it will only do so due to any attempt to forcibly remove it.
  • Super leaping: The Black Mercy's agility, speed and coordination are inhuman due to it being cephalopod in nature, as it is able to outmaneuver a Kryptonian and lunge at them from several feet up.


  • Rejection: If the victim of the Black Mercy rejects the fantasy world, it will slowly detach and die.



Season 1

Season 2

Behind the scenes

  • In the DC comics, the Black Mercy is a parasitic alien plant. In the Superman Annual Vol 1 11 comic, For the Man Who Has Everything, Mongul had a Black Mercy latch onto Kal-El, placing him into a fantasy reality where Krypton never self-destructed.