A complete mystery, the man known as Onomatopoeia first appeared within the pages of Green Arrow. After killing two lesser-known vigilantes, he set his sights upon the Arrow family, seriously injuring Connor Hawke. He later tracked his prey to the hospital to finish him off, but was stopped by a blood-transfer weakened Oliver Queen. After Connor's successful surgery, Onomatopoeia fought the elder Green Arrow, doing quite well never the less being hit with several arrows. Despite falling from the hospital roof during the fight, Onomatopoeia was able to escape before Green Arrow even had a chance to see where he had fallen.
Not much is known about his past except his secret identity has a family and his house has a secret trophy case with the masks of all the super heroes he's killed on display.
In the Widening Gyre series Onomatopoeia was masquerading as a costumed hero named "Baphomet". He made his first appearance when Batman was fighting the Demon Etrigan and helped the Dark Knight by throwing a bucket of holy water on the Demon. A week later "Baphomet" aided Batman, by beating a guy who had kidnapped a little girl, while he jumped to save the girl, Later he appeared while Batman was about to finish the Black Spider, he and Batman spoke and he told Batman he wasn't a native from Gotham and informed him of his name. Batman gave his blessing to work in Gotham as long as Baphomet doesn't kill anyone.
After a few weeks working together "Baphomet" took his mask off in from of the caped crusader, something Batman was not ready for since he feels that involves a higher level of commitment. After that the Batman disappeared on Baphomet in the same fashion he usually disappears on Jim Gordon. Later "Baphomet" filled in for Bruce, along with Tim Drake, while Bruce was in Aspen with Silver St. Cloud. After capturing Mr. Freeze he took his mask off again, this time in front Tim, who was very surprised. Tim gave Bruce a report about that night and spoke very highly of "Baphomet". Days after that he single-handedly took down the Joker. Following the capture, he changed into civilian clothes and went home where he discovered that Batman had been following him. He told Batman that he is married, has a boy and a girl, is a insurance adjuster from Delaware but moved to Gotham before his first was born and most importantly that he started to fight crime when his baby brother Jerry was killed by a masked criminal. After explaining the Batman that all he wants to do is clean the city of criminals for decent people he started to cried, the Batman hugged him. Batman confided in him several secrets that he had never told anyone, such as when he had a bladder spasm after some thermite exploded a little to close to him when he threatened Gotham's crime families. Batman introduces him to Silver St. Cloud. The next morning he kills Silver and reveals himself as Onomatopoeia.
Onomatopoeia shows up during Infinite Crisis, being one of the villains sent by the Secret Society of Super Villains to take over Metropolis. But during the battle Onomatopoeia is seen battling the vigilante Odd Man.
Onomatopoeia, for reasons unknown, assisted the Joker in escaping Arkham Asylum as bait for Batman. He also shot Deadshot point blank in the head but was unsuccessful, overlooking Deadshot's ability to play dead. Onomatopoeia paid Joker to start a gang war against Maxie Zeus who was using Joker's laughing gas as a drug called "Chuckles". Eventually Onomatopoeia fought Batman in an hand to hand fight and lost, he escaped by stabbing the Joker in the heart and leaving Batman to choose either to capture him or save Joker. Batman decided to save Joker's life instead of chasing after Onomatopoeia.
Skills and Abilities
His martial arts skills are quite formidable. He may have meta-human endurance since he was able to fight with several arrows lodged into him. He is also skilled with fire arms such as pistols and snipers, he even engaged Deadshot in a gun fight.
Onomatopoeia speaks only in sound effects, however he has spoken one actual word before, that word being "onomatopoeia". He said this word when a dying superhero ask him "who he was" but she never heard it since he shot her before he said it.