The Banner of Sarleon is an unique Polearm, belongs to King Ulric, Monarch of The Kingdom of Sarleon. It has a small stripe that is the reason the weapon is named Banner, with a Lion on it, as Ulric is proud for restoring the Order of the Lion, which now serve and fight for him.
The Banner of Sarleon is the longest weapon in the mod, surpassing even other long couchable lances (258 range) like Long Knight Lance, but nearly doubling these long lances damage. Having the highest reach means its the safer lance to charge with against other lances that allow Couched lance damage. It's high damage output, along with its decent speed and highest range makes this lance the best one in Pendor by far. This difference is augmented by the lack of lances within the Rune Weapons.
To obtain this weapon you need to successfully defeat and capture the king of The Kingdom of Sarleon (King Ulric). Once this is done, engage on a conversation with him. If his kingdom has 6 or less castles+cities left, he will have a special option in which he trades his unique weapon for his freedom. This will remove the weapon from his inventory meaning the next time you'll meet him, he will use his secondary weapon.
This can only be done if the player is a Monarch.