Blackwall is a Free Marcher Grey Warden who was part of the Inquisition that stopped Corypheus and The Breach.
Dragon Age: Inquistion
When the Breach opened, Blackwall kept the people of the Crossroads safe from demons with no expectation of reward. While Blackwall kept the demons at bay, the villagers fled with supplies from their farms as they fled the danger but were eventually robbed by bandits. Once Blackwall discovered that the bandits robbed the fleeing innocents, Blackwall became furious and rallied some of the farmers in order to hunt the bandits and recover the stolen supplies. Blackwall told the farmers that while demons and Blights were his responsibility, the farmers would need to learn how to defend themselves against such thieves on their own. Inspired by his leadership, the farmers willingly followed Blackwall into battle.
The Inquisitor finds Blackwall in the Hinterlands, where he is training a trio of conscripts to fight off bandits, who attack shortly after. After fending off the bandits, Blackwall sends the conscripts off and is questioned by the Inquisitor over the disappearance of Ferelden’s Wardens. He admits that he knows nothing about other Wardens, as he has been on the road without contact, but refuses to stand idle if his order was involved in Divine Justinia V’s death. Believing his aid could make a difference in restoring the peace, Blackwall offers to join forces with the Inquisition. While in service of The Inquisition, Blackwall is a steadfast companion up through the defeat of Corypheus.
Two years after the defeat of Corypheus, Blackwall is stationed in the Vimmark Mountains. He reports to Warden Stoudenmire who is conducting an ongoing investigation of the Vimmark Prison. He is expected to return to the Wardens after the events of the Exalted Council. After the events of the Exalted Council, Blackwall goes to Weisshaupt fortress to pledge himself to the Grey Wardens for good.
In the years that followed, he was seen faithfully carrying out the duty of the Wardens and helping others along the way. He is present at Weisshaupt during the fall, but his current whereabouts are unknown.