The Nemean Lion is a monster from Greek mythology. The Marvel adaptation was created in 2010 by Colleen Coover. Making its first appearance in issue #1 of the Thor and the Warriors Four comic book series.
The Nemean Lion is a descendant of Set, an Old One. It's the offspring of Set's granddaughter Echidna who mated with Typhon, one of the Titans. The monster has an impenetrable hide. It was one of the "labors" of the heroic demigod, Hercules.