Norscan Ice Wolves
As with all creatures of the Old World, the further north one goes, the more likely an encounter with a beast touched by the mutations of the Ruinous Powers. Marauder Warwolves are one such afflicted beast – like their Warhound cousins, the Warwolf mutation is the result of exposure to the energies of Chaos deep in the malign wilderness of Troll Country where they originate, enabling them to freeze foes in their stride with only their icy breath. Woe betide any unfortunate soul who strays into the Warwolves' territory, who will likely hear their mournful howls before being hunted, frozen, and devoured.
Very Fast: This unit can run circles around most other units, taunting and harrassing the enemy or evading its missile fire.
Frostbite: The intense cold cuts into the flesh and burns the foe's extremities, greatly reducing their speed
Ice wolves are not really good at fighting in front of the melee, the frostbite is useful, but for a pure melee units, use ice trolls.
Ice wolves are made for two things: flanking with their god tier speed and killing fleeing units.
When used as flankers, you need to take down their archers before because they can die very quickly. They can do it, if the archers are not able to strike back in melee. T1 to T3 archers are just fresh meat for them if they don't outnumber the wolves. Be aware of the ranged units who can strike back in melee, however. Wolves have a 15% of missile resistance, but only 15 armor. They are also made of glass in melee. They also have a niche against ranged light cavalry, they out speed them in general, if you have hard time with this type of unit.
But the true purpose of the ice wolves is killing fleeing units. If an infantry unit try to run, and being catches by the ice wolves, basically, they are dead (and it's quick). Frostbite, great speed (95!), the numerous wolves, the charge bonus, good attack and good damage, correct AP and their agility make them really, really better than cavalry in order for killing running enemies. Two packs are really efficient, one right and one left of your army, so you can easily catch everything, except some light cavalry. Probably the best unit of the entire game for this.
They excel against low-leadership armies, and do a good job for the middle-tier. Against high-leadership, they are a bit useless. Don't even try them against dwarfs, you will lose your doggos and you will not be rewarded for this anyway.
Strong armoured monsters can also be a threat for them, even if they are fleeing, high health mean they can survive and get back in fight, and if you don't call the wolves to run away, you risk to lose a great part of them. Especially against units who are especially good at cleaving. Keep an eye on your doggos.
When you have no more archers, artillery and no fleeing units to take down, throw them in the back of the enemy melee. Basically you have probably win and they will finished the job and destroyed any remnants of the other army.
Don't try to use them if you don't want to micromanage. They die in a couple of seconds with a good focus. If you are good at micromanaging shock light cavalry, then you will probably enjoy them.
Dogs are the best friends of the humans. Ice wolves are the best friends of northmen. By far the strongest hound unit.