Hellgar is a notable Hellhound under Sombra's command, and who was sent to hunt down Team Harmony (Ciel in particular) not long after they arrived in England. He was the pack leader of the houndours that attacked them prior to their arrival as well, and the main antagonist of season 2 of Crossover Together.
Hellgar is shown to be rather manipulative and harsh towards those under his command, having little sympathy towards others. If he finds someone not doing something right, he will often threaten violence and/or death, not hesitating to attack and brutally hurt others to get his point across. He is the kind to resort to cheating tricks to get what he wants, including forcing Twilight to be his spy, and sitting out in a fight to let his minions do his bidding for him.
He also hold a sort of racial bias: having little care towards Humans and Homunculus, while showing decent, and even cheeky companionship to his fellow Demons, thinking that a Homunculus can't ever own a slave, and that humans are nothing more than food.
Hellgar is capable of blasting fire from his mouth, which he can use to deadly effect. This same ability he can also use to create a fire wave to deal with multiple opponents.
He is also shown to be able to walk freely through walls in a shadowy substance.
As a species of hellhound, his bite is considered lethal, him describing it in a way that if he did bite someone, that wound will never heal.
Hellgar is able to stretch his pointed tail, and use his end like a spear, easily able to impale a human's skull in one strike.
During his days in the Underworld, he at one point tried to convince Blair to join Sombra in their goal, yet when she refused, Hellgar punished her by burning her home, leaving her homeless and forcing her to leave the Underworld.
After Lust and Gluttony found Envy after another failed attempt to kill Team Harmony, Hellgar arrived on the scene and informs them that he will be taking on Team Harmony while they recruit more demons. Before leaving, he also got Gluttony to leave, telling him there were some slaves in the Underworld getting antsy.
His first involvement began when he found Twilight alone, and held her captive for a bit. After a short discussion, he got her into spying for him, only until she agreed which he released her and left. Upon coming back to her though, he found she hadn't done that, and warned her that if she didn't cooperate, he threatened her life, saying that it was her job to know and then to tell him, before he had to leave when Grell Sutcliff almost found him. His third time finding her, he found she still didn't do it, and gave her a final word of warning that if she didn't give him anything, he will kill not her, but all her friends, making his point painfully clear. Upon finding her for the forth time, he ended up ambushed by the rest of her friends, and he was forced into telling them Sombra's identity before he managed to escape.
Shortly after hearing of the royal ball, he took out his anger on Envy and Lust, killing them multiple times in a fit of rage and blaming them for the failures, only to be stopped once Sombra showed up and assigned him to officially attack them, and that Lust and Envy were under his command from there on. He sent Envy and Lust to the Phantomhive Manor that night, as he and his pack went after The Queen. He quickly made short work of multiple guards, killing dozens in the process, before confronting and fighting Team Harmony head on. He at first stayed back, but was forced into the fight when Team Harmony caught him on it, and it got to such a point when he blasted a fire wave, catching the whole place on fire in a desperate attempt to kill them all. When he found out that didn't work, he gave everyone a primal warning, yelling that they'll all suffer the wrath of the Underworld, before unleashing one more fire blast.
The next morning, Undertaker made a comment that it had been a long time since he made a Dog coffin, implying that Hellgar had died in the fire.
His thoughts towards many humans, and to extension Homunculus, are mainly negative, and he believes that they're nothing more than food to feed his kind. He might have a even lesser thought on Homunculi, saying they can never even own a human slave, and was just as cruel towards them as humans.
He tried to get Yugure to be his spy on both the Phantomhive Manor and Team Harmony, thinking he had control over her. But as time went by, he grew more and more frustrated with her, and finally ditched her near the end of season 2.
It is a bit unclear to his treatment on Sombra, though he is shown to be rather loyal to him, although a bit questionable about his more humble approach towards Homunculus.
Hellgar openly welcomed Sebastian into Tartarus at first, and happily insisted to him to relax and have him serve him, although Sebastian was more used to serving others himself. Hellgar even gave him a meal of a slave's soul when he realized that he didn't eat human meat. However, he considered him a traitor not long after he rescued Team Harmony from the inferno at the palace.
- He's the only Hellhound of his kind showed to be Sentient, as other members of his kind are presented as basic guard dogs. The reason he was sentient while others aren't is unknown.