Echidna is part of Greek mythology. The Marvel adaptation was created in 2014 by Cullen Bunn and William Sliney and made her first appearance in issue #11 of the 1st volume of the Fearless Defenders comic book series.
Background[]
Echidna is the granddaughter of the Elder God Set born to his son Phorcys who mated with Ceto, a sea monster. She has sired many of the monsters of Greek mythology, most of which the heroic demi-god Hercules has battled. Most of them were sired with Typhon, one of the Titans, except for Angerboda who she sired with Varcolac and the Snakes of Many Colors.