The First Hellhound
Kai was a teenage runaway who resorted to thievery in order to survive until he became the most able student of the Armless Master who presided over a secret martial arts dojo in the backstreets of Gotham City. However, Kai never gave up his night life as a thief which brought him into conflict with a young Selina Kyle. Their first encounter took place at a museum when Kai was conducting an Egyptian ceremony with a religious artifact that resembled Bast, a cat-like goddess. Unfortunately, Selina wanted the artifact as a keepsake so she ruined Kai's ceremony by stealing the artifact.
Kai assaulted Selina for her interference while shouting the name "Nehko-Chan" at her but when she regained consciousness, Selina followed Kai back to the dojo for a rematch. Selina bested Kai and the Armless Master was so impressed by Selina's tenacity that he welcomed her as the first woman student in his all male dojo. As time went by, Selina began to show greater promise than Kai but the Armless Master was eventually killed by Lady Shiva which caused Selina to leave the dojo along with the other students.
When Selina became Catwoman, Kai eventually found out and he viewed this revelation as a sign. Kai believed that the only way for him to find peace with himself is for either Selina or for him to die. Kai then became the mercenary known as Hellhound and vowed to exact his revenge for the humiliation that Selina had brought him. After performing another successful heist, Selina is confronted by Hellhound and Kai tries to force Selina into killing him thereby finishing the Egyptian ceremony that Selina had interrupted when they first met. The ceremony was supposed to transform Kai into an actual Hellhound but Selina refused to indulge Kai's request so he decides to carry out his revenge plot. Instead of killing Selina, Kai's face ends up scarred which makes his hatred of Selina even greater.
Hellhound and Catwoman meet up again thanks to the Collector, a relic connoisseur, who wanted them both to steal an artifact called the Wheel of Plagues from an archeological dig. Unfortunately, Ra's al Ghul also wanted the Wheel for his draconian crusade to clense the world of evil. Catwoman and Hellhound reluctantly team up to defeat Ra's' new bodyguard Bane but Bane defeats them and takes the Wheel. After their defeat, Catwoman and Hellhound go at it once again. Catwoman is once again triumphant and Hellhound was left in shame.
Hellhound was later employed by Jackie Pamerjanian, the drug kingpin of Rheelasia, to protect his poppy fields but his employment was short lived thanks to Black Canary who brought Rheelasia's military to Pamerjanian's door step. Hellhound returned to Gotham where he served as Lew Moxon's bodyguard during a summit for all of Gotham crime bosses. When a shootout broke out between the rival gangs, Hellhound didn't bother in protecting Moxon from Philo Zeiss as Zeiss lunged at his former employer. Hellhound was more concerned in attacking Kwan Lin, the head of the Gotham Triands.
Hellhound must have developed or already had ties with Yakuza clan in Gotham and killing the leader of the Gotham Triads would be a great honor. Hellhound was last seen lunging at Kwan Lin as she fired her gun in his direction. With all the gunfire, it is unknown if Kwan Lin delivered any shots that could have fatally wounded Hellhound or for that matter if Hellhound was successful in killing Kwan Lin. When the police arrived, they found Kwan Lin's body far away from Hellhound's. However, i ts possible that NKVDemon and Hellhound killed each other since their bodies were in close proximity of each other but how it was done remains unknown.
The Second Hellhound
Hellhound II bought his costume from the Calculator and became a member of the Society as well as Calculator's bodyguard. Hellhound was captured by the Suicide Squad and exiled to the prison planet, Salvation, with the second to last batch of criminals. When Hellhound arrived on the planet, he ended up getting wounded by a robotic creature and then he is sacrificed by the Body Doubles to the "Lion-Lizards" so that they could make a quick escape.
The Hellhounds of El Paso
In El Paso, a "title match" was being held where Devil Dog, Chifford's cousin and Anubis, an unknown dog-like metahuman, fought for the right to be called the new Hellhound. However, their fight was interrupted by the Blue Beetle and the disgraced fighters formed a team called "The Global Ultra-Society of Dread" in order to defeat the Blue Beetle. Anubis and Devil Dog were beaten once again by the Blue Beetle. They renamed their team name as "The Dog Pound” and joined Tapeworm during his failed ambush on the JSA. It's possible that Anubis performed the same ritual that Kai was attempting in order to become a true hellhound.
He is a skilled martial artist and the first Hellhound (Kai) was trained by the Armless master , the same master who trained Catwoman. Hellhound is extremely skilled with knives and throwing them. He also trained dogs to serve him.
Hellhound appears in the "Justice League Unlimited" episode "Grudge Match". He is shown as a fighter in Roulette's Metabrawl fighting Shatterfist.