Black Mercy

Black Mercy is an alien parasite.

Biography
It was used by Non to subdue Supergirl in order to proceed with the Kryptonians' plans uninterrupted. When Alex Danvers successfully freed Kara from the Black Mercy-induced fantasy, the creature detached from Kara.

Powers and Abilities

 * Unique Physiology: 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. Instead, the host must reject their fantasy.