Reik

Reikr (old Norse: "chieftains", "kings") are in effect the strongest of all Norse units, and are primarily super-heavy axe infantry and thus have both an armour-piercing attack AND an anti-building role. They are slow and powerful units, capable of holding their own in most situations with proper backup - otherwise, however, they are easy prey like most Norse units for any faction with good ranged units, especially Horse Archers or Javelin Cavalry, owing to their slow gait and high costs.
A Reik thus is best used offensively, using his immense LOS to guide and inspire inferior melee units to "hold the line", being able to see far - not only is he available the moment a Warrior Hall is installed, but his LOS improves too with each level of Culture researched. Yet his prohibitive cost means that you cannot train as many of these units as you normally would have. Equally, Reikr are trained slowly, so you need to be careful how you use these units — the Reik is best used as a support unit who can with support turn the tide of a battle with other units. Because they are available only for the Norse, you may well be hard pressed on how to defend these units from cavalry. As a result, the Reikr is best used in environments Norse armies are familiar with — broken ground with lots of rocks and very little room for cavalry to manoeuvre. Otherwise, you are advised to ignore their use, and instead seek a more versatile build, such as a combination of other Norse units with your Germanic mercenaries to keep your armies going.