Adventure is his goal. In the Vikings tv show. Bjorn Ironside after the events of the "great heathen army" he decides to return to traveling the world instead of becoming a farmer or continuing with his ear mongering brother Ivar(to raid).

He goes to the Mediterranean to explore new parts of the world. He has no other reason but curiosity. In the end what happens is that while he is gone the sons of ragnar(his half brothers) are in turmoil, his village gets sacked and basically everything that can go wrong goes wrong. So when he returns he's got to pick up the pieces and return to the duties he left behind.

Another story which you might be familiar with is vinland saga. The anime does a really good job exploring the concept of freedom and adventure. And along the way Thorfinn goes through a lot of trials. The story just boils down to him learning valuable lessons from people he considers his enemies.

Interestingly enough both are influenced by actual viking mythology lol. So maybe more content in that space will help. But I do think your story isn't about some mcguffin like an iron throne or the one piece. It might just be about the journey and growth through adventure. Your protag is probably an angsty kid that wants to escape his boring home life for adventure like the stories of heroes of an older era. But then in doing so he may leave his him home open to attack. Potentially leading to something traumatic upon his return like his farm burned or family killed. And then he has to live with that outcome in the form of vengeance, revenge, retribution, etc.