One of the major events of Vinland Saga is the heroic last stand of Thors, the mightiest Viking warrior. This popular seinen series explores themes such as revenge, finding the true purpose in one's life, war vs. peace and much more. Thorfinn's strained relationship with Askeladd is a good example of that.
Thorfinn grew up as a cheerful and happy boy, living with his parents and older sister Ylva in a peaceful town on the Icelandic coast. All that changed when Thorfinn snuck aboard Thors' ship to see the world and witnessed his father's gruesome demise firsthand as a boy.
Thorfin Learned to See War For What It Is
Fans of the Assassin's Creed game series who are looking forward to the AC: Vahalla title might recognize what is going on here. It is the early 1000s in medieval England and the land is at war. (In fact, Vinland Saga is greatly educational about what that time period was really like.) The brutal Vikings sail the high seas, plundering and waging war anywhere they like in the name of their gods and honor alike. As a boy, Thorfinn longed for glorious combat to slay his enemies. But when he got a real taste for it, he realized that war is cruel, ugly and pointless, and the violence never brings anyone any happiness. He first learned that when Thors was surrounded and killed, and he continued to learn that lesson as he traveled with his father's own killer, the Viking band leader Askeladd.
Thorfinn hated Askeladd for what he did, but then again, he wanted to get revenge on Askeladd in honorable combat, not through assassination or fighting Asekeladd 100 vs. one. Instead, Thorfinn learned much from his new father figure as they traveled across war-torn Europe, and Thorfinn was there for some of the bloodiest battles of all. He and Askeladd saw a lot of carnage, and neither of them took any pleasure in it. In fact, Askeladd hated the Vikings and their way of life, identifying much more with his Welsh ancestry than his Viking half. Askeladd's detached view on war and lack of interest in honor may have influenced Thorfinn's own thinking in many ways.
Thorfinn wanted revenge, not glory in Valhalla and Odin's praise. More than once, Askeladd spoke to Thorfinn about the true nature of war, the afterlife, the Vikings and honor, and Askeladd listened carefully. If it weren't for Askeladd, then Thorfinn might have grown to enjoy war after all, and fight in the mighty god Thor's name, not in the name of peace or justice.
Asekladd's Fate Changed Thorfinn's Future
Thorfinn's relationship with Askeladd was defined mainly by a thirst for revenge, but in an odd (and later fruitful) twist of fate, Askeladd denied Thorfinn his chance for revenge by losing his life at someone else's hands. In the climax of the anime's first season in 2019, Askeladd, Thorfinn and prince Canute of Denmark stood in the Danish king's court where Askeladd finally revealed his disgust and hatred of Vikings, and slew the king where he sat. Naturally, this turned everyone against him, and prince Canute was the one to dispatch Askeladd by the sword. Thorfinn's revenge was suddenly impossible, and he had nothing left. He thought his life was over.
But not so. In dying, Askeladd gave Thorfinn one last gift: the opportunity (and reason) to seek a new path. This parting gift didn't feel like one at first, since Thorfinn was distraught and he ended up being sold into slavery (ending up on Ketil's farm in Denmark). However, Thorfinn had gained absolutely nothing out of war or fighting by Askeladd's side, and when he was drained of vengeful feelings, Thorfinn was more receptive to new ideas.
As the years passed, Thorfinn lost his taste for war and began to seek peace. He became a pacifist, an oddity in his time, and he longed to find and found Vinland, a peaceful land of vineyards and happiness across the vast ocean (Newfoundland). That was the legacy of Thorfinn's and Askeladd's relationship: that seeking peace and happiness, and building wonderful new things, always trumped fighting and killing in Odin's name.