- For the rabbit known as Gary Jr. II, see Gary Jr. II.
- "Uh, no, sweetheart. I'm the Canine of Chaos. I was gonna have you murder each other, but now I'm gonna kill you myself!"
- —Marchosias to Astra Logue[src]
While in Hell, Gary Green noticed Marchosias in the form of a terrier and, believing he was lonely, decided to adopt him. As he was being introduced to the Legends by Gary, who explained that he was not trained, Marchosias urinated on the floor and ran away.
Sounding like barking to each member, Marchosias had different Legends do his bidding. He had Charlie move the rings of the Loom of Fate and drop them into the ship's septic system; meanwhile, Zari Tarazi and Nate Heywood sabotaged the Waverider as the dog yelped. The Legends had no memory of their actions.
Gary carried the terrier to Sara Lance, hoping the dog would cheer up his blind commander. While she was holding him, Marchosias tried to persuade Sara to kill Gary, but she was able to reject his prompts. Soon he transformed into his true form but John Constantine was able to stun him. The hellhound escaped to confront Heatwave and his daughter but was thwarted by Sara. Constantine told Sara that he needed the real name of the hellhound to banish him when Astra Logue arrived providing it. Constantine then cast the spell that opened a portal, sending Marchosias back to Hell.
In one erased future, the Legends were all killed by their leader, Sara Lance, who was under the control of the terrier when doing this. This was all initially started when Gary brought Marchosias in to cheer Sara up and he used this opportunity to mind control Sara into snapping Gary's neck.
Another erased future was seen by Sara in a vision where Marchosias, in his hellhound form, killed Mick when Mick was trying to protect Lita from the creature. Both of these futures were prevented when the Legends realized the creature's scheme.
Powers and abilities
- Hellhound physiology: As a Hellhound, Marchosias has special powers.
- Fire immunity: As demonstrated upon being shot by the heat gun, because Marchosias was born from fire, fire cannot hurt him. If anything, it makes him stronger.
- Mind control/Telepathy: Marchosias can make anyone do his bidding just by talking, though it would appear that only the being he is trying to manipulate could hear him speak the incoherent language; to anyone else, he is simply loudly barking. He is seen to be powerful enough to control a deity like Clotho, but it would appear that he could only control one person at a time. Anyone under this effect would be in a trance-like state and thus would not be able to recount anything that's happened whilst under his influence.
- Shape-shifting: Marchosias was able to shape-shift into a Jack Russell Terrier.
- Immortality: As a Hellhound, Marchosias is immortal.
- Banishing spell: For Constantine's spell to work, he needed to know the real name of the demon; fortunately, Astra knew the real name, causing the Hellhound to return to Hell.
DC's Legends of Tomorrow
Behind the scenes
- In demonology, Marchosias is a powerful marquis of Hell, commanding thirty legions of demons.