Banners, then and now, are often a curious amalgamation of plain communication and naked aggression. They’re well-known as heraldic devices, displaying a coat of arms to identify one side to the other on the battlefield, usually just before they were about to attack each other. However, they’re also just a means of communicating who or what a place or thing belongs to. If you’re shipwrecked, the flags on the boat responding to your frantic SOS can tell you where you are and who is about to rescue you. Even today, flags are used this way. Ships still use flag signalling to send messages without the need for radios. Warships still hoist battle ensigns, huge flags to stand out in the smoke and chaos of a pitched battle, showing that a ship is ready to fight, and which side it’s on.
In The Banner Saga, every clan, including your own, has a banner that flies overhead as you travel. But there isn’t as much talk about the clan’s actual, physical banner as there is about what it represents: forging unity from the lack thereof, creating a clan rather than fighting others, and the rite of passing on stories to later generations.