Northern Fury is a 22 page booklet published in a similar style to the main rule book and is accompanied by four cardstock battle boards. The supplement introduces four new factions - the Anglo Saxons, the Bretons, the Jomsvikings and the Scots - along with an new scenario. The first three factions utilise the same dice as factions from the original rules but the Scots have their own new dice (assuming you are bothered about the custom dice).
Each faction has a brief introduction, any special rules, new Heroes and the faction's specific abilities which run to around four pages per faction with a few accompanying photographs of appropriate figures.
Superficially, the Anglo Saxons are geared around large levy units, the Bretons javeline armed cavalry, the Jomsvikings have a variable level of "Wrath" which enables/enhances various abilities and the Scots spear armed infantry; however, each faction looks like they have their own playing style and each differ from the others and the original four factions.
The scenario, Wooden Oaths, is designed for two teams of players and looks interesting.
Since I have figures for some of these factions already and am particularly interested in the Anglo Saxons and the Scots I though this would be a useful addition to my Saga collection.
I see another supplement is due out shortly and has some Irish too ....