The Secret Six was originally formed by Mockingbird - a team of underground operatives serving the goals of covert US-government group, the Agency.  They have operated. . . MORE >

The Secret Six was originally formed by Mockingbird - a team of underground operatives serving the goals of covert US-government group, the Agency.  They have operated for decades in various incarnations. 

The third incarnation of the Secret Six was a villainous one, appearing just prior to Infinite Crisis.  Lex Luthor gathered a sextet of villainous characters to sabotage the efforts of the Secret Society of Super Villains.

The Batman Who Laughs' Secret Six:
In the 2019 Batman/Superman series, The Batman Who Laughs uses Joker toxin-laced Batarangs to create dark and twisted versions of six individuals necessary to open a portal to the Dark Multiverse, those being Commissioner Gordon, the Blue Beetle, Shazam, Donna Troy, Hawkman, and Supergirl.