Rattler was a villain who was an enemy of the Rawhide Kid, an Old West hero from Marvel comics.
The Rattler was a highly skilled athlete, gymnast and aerialist. He was incredibly quick and rather strong. He was also an experienced horseman and marksman. The Rattler had suffered an injury which left him no longer able to perform his acrobatic feats at the circus that he worked in.
Heath Benson was a onetime aerialist whose career ended after injuring himself in a performance. Benson became a ringmaster for the circus after this, but was jealous of the aerialist Whirlo, remembering his old role. To recapture the glory of his earlier career, he assumed the guise of the Rattler and performed daring acrobatic stunts as he robbed locals, both for the glory of astonishing onlookers, and to frame the innocent Whirlo for his crimes.
The Rawhide Kid fell for this ruse and suspected Whirlo as being the Rattler. When he confronted the aerialist he was bested in combat before realizing his mistake. The Kid then went on to defeat and unmask the real Rattler, and sent him to prison. The Rattler soon escaped, however, and when Whirlo heard of this he decided to commit crimes dressed as the Rattler in order to frame him for revenge. Dressed as the Rattler, Whirlo robbed Tombstone of $10,000, and nearly set the Two-Gun Kid after the real Rattler, until he slipped up, accidentally mentioning the amount the Rattler had stolen before it had been made public. Whirlo was then apprehended and sent to prison.
Whirlo's activities succeeded in drawing the real Rattler to Tombstone, where he joined Iron Mask's gang alongside several other costumed outlaws. The Avengers West Coast had travelled back in time to Tombstone and were able to assist the heroes of this time, Phantom Rider, Rawhide Kid, and the Two-Gun Kid in stopping the criminals reign of terror and capturing them. The Rattler had attempted to ambush Tigra, who quickly overpowered him and launched him at Hurricane, knocking out both villains.