WARNING: The following article contains spoilers for Avengers #17 by Jason Aaron, David Marquez, Erick Arciniega and VC's Clayton Cowles, on sale now.
The roster of the Avengers is almost always in flux, with members joining and leaving the team at a moment's notice. The newest iteration of Earth's Mightiest Heroes assembled once again with Captain America, Iron Man and Thor deciding to reform the Avengers alongside Black Panther (the team's chairman), Captain Marvel, Hulk (Jennifer Walters), Ghost Rider (Robbie Reyes) and Doctor Strange.
Blade would step in for Doctor Strange to aide the Avengers against a new vampire threat called the Legion of the Unliving, but the Shadow Colonel's deadly team has succeeded in sparking a vampire civil war. After Shadow Colonel was able to force Ghost Rider to succumb to his more demonic urges, the Avengers looked for some heavy-hitting backup by recruiting a faithful four-legged sidekick as its newest member.
Man's Best Friend
In the last issue of Avengers, the Legion of the Unliving multiplied its ranks by unleashing a swarm of rats into a Russian prison, with vampire blood strapped to the backs of the vermin. Once the rats exploded, the tainted blood created new footsoldiers for the Legion of the Unliving. Of course, the Avengers joined the melee to assist Russia's own super-team, the Winter Guard, with both sides fighting to a standstill.
Though they're all vampires, one member of the Legion of the Unliving stands out from the others, and its the demonic dog with a skull for a head: Sarge. Not much is known about Sarge, but he had enough psychic power to make Ghost Rider turn on his teammates. In turn, it looks like the Avengers decided it takes a dog to beat a dog, which is why they brought in Thori, Thor's Asgardian dog.
Thori rushes in to pick up the save on Hulk before Sarge can really sink his teeth into the Jade Giant. In the main event match to see who is the Best Murder Dog in the Marvel Universe, it's Sarge vs. Thori. Unfortunately, Avengers #17 doesn't focus entirely on this showdown, but the heroes do win the day, though the Legion of the Unliving are able to escape after Hulk undergoes a gamma explosion.
However, once the dust clears, we see Thori standing over the unconscious body of Sarge, pronouncing, "Thori King of all dogs!" Marvel is on a roll recently with superpowered canines -- along with Thori is Venom's symbiotic pooch, Cosmo from Guardians of the Galaxy and of course, Lockjaw of the Inhumans.
Thori may have only guest-starred in Avengers, but with its roster continuing to grow with Black Panther's Agents of Wakanda, there is no reason Thor's dog shouldn't show up again to lend a helping paw.