During the events of the Fall of the Scarlet Enclave, Landgren is first seen in New Avalon with Abbendis, Commander Jordan, and Torturer LeCraft. Towards the end, after the Destruction of New Avalon and the Fall of Tyr's Hand, he is seen at King's Harbor, again by the side of High General Abbendis. He was present when she disbanded the Scarlet Crusade, and is therefore considered one of the original founders of the Scarlet Onslaught.
As the Scarlet Onslaught gained a foothold in Northrend, Landgren's status rose dramtically; he was now considered the highest-ranking leader in the entire Scarlet Onslaught, only second to Abbendis herself.
When Abbendis was killed by adventurers in New Hearthglen, Landgren was elevated to the rank of Archbishop and assumed command of the Scarlet Onslaught. However, his behavior changes with the reappearence of Grand Admiral Barean Westwind (actually the dreadlord Mal'Ganis in disguise.) He places all his loyalty in Westwind and created the Onslaught Raven Priests.
He was at first believed killed after he jumped off a cliff, but is later revealed to be still alive at the Crimson Cathedral in Icecrown (via resurrection.) Adventurers manage to kill him again, and Lord-Commander Arete, a Knight of the Ebon Blade, destroys his spirit, thus preventing him from being resurrected ever again.