Avitus's greatest weapon is his unmatched hatred for the enemy particularly non-humans and Guardsmen. Since the campaign on Victory Bay, he has unleashed his weapons with a new fury attributed to the time he fought against traitorous Guardsmen. Many of his squadmates did not survive the fighting, something that changed Avitus forever. He has thought Guardsmen as weaklings and traitors to this day until he stood with them against the Tyranids, then he recognized their fighting spirit. Still, it would be unwise to arouse his fury as he is known to destroy everything in his path in such a state. Avitus' squadmates often said that they did not fear the enemy but feared Avitus' rages.
Avitus and his 2 squad members are effectively Tactical Marines from DOW 1 that all carry Heavy Bolters by default. They have setup and teardown time and can put out quite a withering amount of fire especially when activating their ability that increases their firing rate. Avitus gets the options for various heavy wargear including a massive pulse cannon that is highly effective against vehicles and buildings (including destroyable structures) for his main gun (while his two squadmates keep their heavy bolters), and a supplementary shoulder-mounted rocket pack that can fire devastating missile barrages at long range. He is VERY weak in melee and somewhat fragile in general, but if you can get him set up and keep melee units away from him, Avitus and his team give ranged damage output matched only by Davian Thule's dreadnaught and are an excellent choice to bring along in every mission that you can.
Depending on the player's choices and deeds made during the missions, as well as choices of wargear, Avitus could be revealed as the traitor within the Blood Ravens. The root of Avitus' corruption and subsequent betrayal began after the Kronus campaign. As much as he hated the Imperial Guards, he saw the Chapter and the Imperium as corrupt and deserving of his wrath, in part initiated by Chapter Master Kyras reveling in the slaughter of Victory Bay and then tasking Avitus 'to be his man in 4th company'. After being revealed as the traitor, the Force Commander led a mission to kill Avitus, now equipped with Terminator armor, a Cyclone Missile Launcher and Assault Cannon.
It is revealed in Retribution that Avitus is considered the canon traitor and that it was Tarkus who slew him. This is referenced when Tarkus revealed himself as The Ancient while in the Judgment of Carrion and mentioned to Captain Diomedes how he was turning into someone who served alongside him on Kronus, during the Tyranid invasion, and how he became corrupted after Kyras called for him. Only Avitus and Tarkus served on Kronus in the Force Commander's squad and so it is heavily implied that Avitus was most certainly the canon traitor.