Darkdevil is in reality the offspring of Ben Reilly and Elizabeth Tyne. Once he began to enter puberty powers like those of his father began to appear however for some reason he began to go through the clone degeneration process like many of the other clones created by the Jackal. It wasn't until he was discovered by Spider-man's first clone Kaine became aware of his degeneration that Reilly got help. Kaine took him and placed him inside a tank that would regenerate his DNA and slow the process so he could be fixed.
Some time later the hero Daredevil was injured and killed in an attempt to save Kaine. He took him to the same complex and stored Daredevil in a tank like Tyne's. Kaine later summoned the demon Zarathos. He wanted the demon to heal the both of them to re pay his debt to Daredevil and save his nephew. However the demon betrayed him and attempted to possess Reilly, but Daredevil's soul that had not crossed over fought and banished much of the demon from Reilly's body. However as a result both Daredevil and a piece of Zarathos remained in Reilly giving him and inhuman appearance and greater powers. He also has a more grown up human appearance and looks older than his right age.
Darkdevil was created by Tom DeFalco and Pat Olliffe and first appeared in Spider-Girl Vol.1 issue 2 (1998).
Major Story Arcs
Reilly soon learned via meditation that he could turn himself from a demon form to his human state. Due to Daredevil's soul inside him Reilly chose to follow in his footsteps and went to school to learn law and became a lawyer and even more became a crimefighter as Darkdevil. However Darkdevil is not quite like either his father nor Daredevil and is quite violent and grim in his super hero career. During this time he found out that Peter Parker's daughter May had become a super hero as Spider-Girl. Although keeping his secret he tried to make her believe she was not cut out to be a hero but she did not back down and soon they often began to work with each other.
Darkdevil also acted as Wilson Fisk's (now imprisoned) counselor in an attempt to stop his control of the underworld from the inside. He even worked to stop the Kingpin from taking over the race for mayor. However the event cause Darkdevil to once again confront the demon Zarathos. He had been using the Scrier Prime as a host and the two foes did battle. Despite suffering wounds Darkdevil beat the demon.
Darkdevil as Reilly attended the wedding between Normie Osborn and Raptor. During the wedding Fury attacked the gathering and forced Normie to bond with the Venom symbiote. Despite help from the Human Torch the two escaped. Spider-Girl later found the two and Darkdevil showed up to help. However Venom surprised him and ran his claws through his chest. However he didn't outright die and in-fact the wound released a type of hellfire which Venom described as both freezing and burning and the suit didn't quite fully heal for some time. Spider-Girl webbed up Darkdevil's wound and took him to the HQ of the new Avengers in hopes they could heal him.
They contacted both the current and past Sorcerer Supremes Doctor Strange and Doc Magus. Both realized they needed to enter his body and fix the real problem. Upon doing so they found that the wound had unbalanced the forces fighting inside Darkdevil and Zarathos tried to dominant both Reilly and Daredevil. Reilly guided the two magicians in his soul and they helped stop Zarathos and Daredevil and Reilly once again united taking control. After a few months off, Darkdevil returned with Kaine and Spider-Girl to help stop a gang war that had errupted between the Black Tarantula and the former Maggia boss, Silverback. During a final battle on Silverback's estate, it was revealed that the Hobgoblin was the true mastermind behind the gang war and Darkdevil was badly injured after fighting both Silverback and the Hobgoblin. He was saved with several other heroes by Spider-Girl before Mayhem finished off the Hobgoblin and his men and Silverback and the Punisher took each other out. He has since returned to crime fighting and his studies of law and is preparing to take the bar.
Last Hero Standing
Darkdevil once again appeared . He had been on patrol when he found Spider-man brutally beating some thugs. Noticing that something seemed to be wrong Darkdevil tries to reason with Spider-man but he attacked Darkdevil seeing him as a threat. However Spider-man's behavior was caused by Loki who had kidnapped many heroes including Spider-man and infused them with dark magic to make them violent. Super heroes both controlled and free from his control arrived to stop the fighting and soon the Hulk was controlled and Darkdevil was one of the many heroes who fought him. Soon however Captain America freed the heroes and Thor banished Loki.
Being the son of a clone of Spider-man Darkdevil has powers like his. He has enhanced super strength, agility and speed. He has a "spider-sense" to warn him of danger and the power to stick to walls. Since apart of Zarathos is inside him he has a demonic appearance and powers some what like Ghost Rider's. He can teleport by engulfing himself in flames and vanishing. He can create hellfire and use it to make constructs often times billy clubs. He can also make energy blasts with his hellfire. He can also recover from injuries much faster than humans via both his spider and demon powers.