Ethereal units like the Spirit Host have a handy additional bonus - you just cannot stop them from moving.
This is especially useful for some ethereal units like the Spirit Host because it has a movement of 6. This unit can therefore move over any terrain features without penalty and is not affected at all by magic spells or effects that usually restrict units in some way. This even includes the devastating Pit of Shades spell that usually sucks low initiative units down into a muddy gaping abyss of oblivion (irrespective of their toughness, wounds or armour saves). PS. can you tell that I like the Pit of Shades spell ? :)
Ethereal units cannot be hurt by hand to hand attacks or by missile fire unless it is magic in nature. This benefit does not extend to the whole combat resolution though, enemies can still win these thanks to rank bonus and other combat round modifiers.
When a Spirit Host comes up against an enemy which outnumbers it, is highly ranked and includes a standard bearer it could be in big trouble and can lose wounds (to lost combat resolutions) at a disturbing rate.
The trouble with the Spirit Host is that is has low strength 3 attacks. If it's ethereal blades ignored enemy armour then this wouldn't matter as much but ethereal blades to not possess this quality.
Spirit Hosts act a bit like swarms in that they can be difficult to shift. However, the whole of the Vampire Counts undead army is a bit like this and Spirit hosts are quite expensive at 65pts for 4 wounds and 4 attacks.
So, what you have here is not a battle winning unit or a unit for defeating good rank and file troops or even holding up cavalry much. What the Spirit Host brings to the Vampire Counts army is a tactical advantage.
What I most like about this unit is it's ability to traverse the battlefield without taking bow fire casualties (although beware of Wood Elves with magical arrows like the Hail of Doom !) The spirits make excellent flankers, not to charge rank and file units in the side but to get around the back of armies to their artillery pieces and to dispatch skirmishers, scouts and other missile unit troops on the way.
Slow moving enemies will have particular trouble dealing with this unit. Once in the rear echelon of a Dwarf army, the Dwarf's artillery will be seriously threatened.
Not only that but, if the enemy expect to be facing a spirit host unit then it might be wasting valuable points on magic weapons and spellcasters to try to destroy the ghosts. Many of these weapon bonuses can be negated and result in a waste of points for the enemy if you just make sure your Spirit Host unit is one of the last (if not the very last) units to be deployed. Put them on the opposite side of the wargame board from the enemies most likely to have the magical attacks and watch your enemy waste valuable turns trying to hunt down and corner your Ghosts.
In in all, I do like the Spirit Host. They give your enemy something else to worry about, especially if he/she has not got much in the way of magical attacks. You can let your Spirit Hosts freely wonder the battlefield (although they would benefit from having a Vampire within 6 inches to allow them to march move - maybe a flanking Varghulf for help) and they can make a real nuisance of themselves.
Next up... Fell Bats.
Image is © Games Workshop Ltd. All rights reserved. Used without permission.