Gunnar commanded the 1st Great Company, and was known to have a poor relationship with Leman Russ. Nonetheless, Gunnar was present at both the Council of Nikea and Burning of Prospero alongside his Primarch, Leman Russ. He later again fought by his Primarch's side at the Battle of the Alaxxes Nebula. During this battle, Leman Russ became demoralized and isolated himself, forcing Gunnar to take command of the crumbling Space Wolves. Gunnar began to slowly lose faith in Russ, but when the Primarch appeared once more to lead his Legion he was reinvigorated. During the final breakout attempt from the Alaxxes Nebula, Gunnar sacrificed himself and his own ship Ragnarok to destroy the Alpha Legion Battleship Delta, allowing for the Space Wolves to escape.