Within Marvel Comics, nearly all of the various mythical pantheons exist. As the Greek God of War, Ares is naturally part of The Marvel Universe. Ares spent much of the modern era amusing himself by pitting Earth's nations against each other. The God of War also found great enjoyment in tormenting his half-brother, Hercules. Eventually, Ares grew tired of his endless warmongering and settled down on Earth.
Relinquishing his title as The God of War, Ares decided to live a human life as a carpenter. Still, Ares retained his skills, weaponry and immortality. At one point, Ares had a son named Alexander, who developed the ability to generate fear in others and see into the future. Together, Ares and Alexander lived an ordinary life on Earth.
During the Ares limited series, by Mike Oeming and Travel Foreman, the titular character had his whole world turned upside-down when Alexander was kidnapped by Mikaboshi, aka The Chaos King. This malevolent entity warped Alexander's mind and trained him to be the new God of War, one who would turn against the gods of Olympus. During an intense battle with Mikaboshi, Ares worked with Zeus to save Alexander. Once Ares' son was free of Mikaboshi's control, Alexander killed the sinister deity with the famed grasscutter sword. Despite their victory, the gods' home of Olympus was destroyed and Zeus was killed. After their victory, Ares and Alexander resumed their lives on Earth.
After becoming a construction worker, Ares was approached to join The Mighty Avengers. Following "Civil War," this team was a group of registered superheroes who worked for the U.S. government. As part of The Mighty Avengers, Ares fought alongside heroes such as Iron Man and Ms. Marvel.
Although Ares' morals were a bit looser than the other heroes', he brought some raw power to the team, standing in for both Thor and Wolverine in this sense. Ares helped The Mighty Avengers fight threats such as Ultron, Doctor Doom, The Hulk and a massive Skrull invasion.
Alexander, meanwhile, was recruited into Nick Fury's Secret Warriors. This group was comprised mostly of young superhumans who had supervillain parents. Together, The Secret Warriors were trained to fight off the Skrull invasion. Afterwards, the team waged a long and difficult war against HYDRA. Alexander was given the codename Phobos, and, with approval from the gods, became The God of Fear. Although Ares was initially furious that Alexander had joined The Secret Warriors behind his back, he ultimately approved, so long as Fury watched over his son.
Following the Skrull invasion, Ares joined Norman Osborn's Dark Avengers team. This team consisted of villains such as Venom and Bullseye, disguising themselves as heroes such as Spider-Man and Hawkeye, respectively. At first, The Dark Avengers were a fitting group for Ares, since everyone on the team was quite ruthless in their methods. Yet over time, Ares began to see Osborn's hidden, sinister machinations.
When Osborn initiated a siege on Asgard, he convinced Ares that Loki was manipulating The Norse gods' behavior. Later on, however, Ares discovered that Osborn had lied to him, enraging The God of War. After angrily attacking Osborn, Ares was brutally beaten by The Sentry, who ripped the Olympian in half.
Afterwards, Phobos joined The Secret Warriors in a final strike on HYDRA's base. During their retreat, The Secret Warriors were cornered by Baron von Strucker and The Gorgon. Buying his team time to flee, Phobos faced The Gorgon in one-on-one combat. Although Alexander fought bravely, he was ultimately killed by the deadly mutant. Returning to Elysium, Alexander was reunited with Ares in the afterlife.
While Phobos has yet to return, Ares has made his way back into the pages of Marvel Comics. Ares briefly returned during "Chaos War," resurrected by the Chaos King so that the two could fight. Ultimately, The Chaos King's power overwhelmed Ares, and he was returned to Elysium. It wasn't until 2015's Contest of Champions #2, by Paco Medina and Al Ewing, that Ares returned for good.
When The Collector and The Grandmaster faced off in a tournament using various champions, they used the rare Isotope-8 to resurrect and bring Ares into the competition. After surviving many battles, Ares returned to Earth and formed the Champions of Europe with his fellow contestant, Outlaw. This new team fought off HYDRA during "Secret Empire" and Malekith's forces during "War of The Realms." Ares' journey may have been dark and tragic, but his return opened up a more optimistic window for the character.