Cairn Wraiths

Cairn Wraiths is a Vampire Counts melee infantry unit in Total War: Warhammer. Extremely effective in battle, the Cairn Wraith has no corporeal form, making it extremely difficult to kill with conventional weaponry.

Description
Cairn Wraiths are hooded, spectral creatures that dwell in the realms of nightmare, haunting the dreams of men. They are amongst the most dreaded of all Undead. Lacking physical forms altogether, they cannot be cut down by axe, sword or hammer blow. Even the strongest faith cannot banish such creatures easily. Worse still, the icy touch of a Cairn Wraith drains the essence of mortal men. A Cairn Wraith is capable of reaching into the body of an adversary and closing its freezing claws around the victim's vital organs, sending painful chills right through a man's soul. Because they are impervious to physical weaponry, only the raw energies of magic or a well-placed blow from an enchanted weapon can slay a Cairn Wraith. The crippling fear that arises from having a nigh-unkillable spectre scythe down any too slow to escape causes even brave men to quit the field. Those who do resist the urge to flee find their return blows passing through the Wraith's incorporeal form. It is well that such creatures are so rare, for these silent assassins are quite capable of slaughtering their way through an entire garrison over the course of a single moonless night.

Strategy
Cairn Wraiths are valuable units in the Vampire Count arsenal. They're able to survive better than most other Undead units, deal an impressive amount of damage and are capable of making many units rout in short order. In general, you want them going toe-to-toe with the enemy's infantry units, and they can be used in pairs to flank enemy troops fairly easily. They make for an excellent anti-archer unit, often being able to ignore most attacks, before rapidly closing the gap and taking them out.

When facing Cairn Wraiths, it's important to play against their weaknesses. Magical Damage will ignore their biggest defense, and can very quickly wipe them out, as Cairn Wraiths lack much health and have no armor. Surprisingly, Cavalry units can do quite well against them as well, throwing the Wraiths back, and then leaving before they can retaliate. Lastly, using magic can often take out Cairn Wraiths in just a couple spells, or cripple them enough on the first spell to have infantry finish them off.

They also come in unit sizes half that of grave guards for about the same cost, so its not practical to build your infantry line with them. Mix a few in to punch through armoured enemy units while filling out your line with larger units.

Because of their physical resistance and armour-piercing melee damage, they are surprisingly good at fighting Dwarfs who obviously cannot use magic and so the biggest threat to Cairn Wraiths is automatically removed from the battlefield. Even though the wraiths deal magic damage and Dwarfs all have innate 25% magic resistance, they are still able to cut through Dwarf infantry effectively while also absorbing most missile/artillery damage better than Grave guard would.