I think they could be used in at least four scenarios:
1) Defending a point or points on the battlefield against all comers if the battle has two sides, fighting whoever attacks them.
2) Defending a point or points on the battlefield against a single opponent.
3) As a "wave" passing across the battlefield, again attacking anyone who gets in their way. This idea based on this link -
http://lotr.wikia.com/wiki/Army_of_the_Dead specifically the bit which says "Aragorn led the Army of the Dead through Lamedon and Ciril. As they went through the lands of Gondor, they found them deserted, since everyone who hadn't gone to war fled the approach of the dreaded "King of the Dead". Even the men of Umbar and Harad, who had been attacking the fords at Linhir above the mouth of the river Gilrain, stopped fighting and ran off in terror." So the dead are on their way elsewhere and pass through an ongoing battle.
4) As a "wave" passing across land, opposed by a single army. The battle ending when one army reaches it's breakpoint or the last (or first?) unit of ghosts exits the far edge of the field.
In all cases there'd be no need for ghostly characters as the ghost units would more or less act on initiative, advancing, say, 20 or 30cm per turn in scenarios 3 and 4. Although if you wished for a "normal" ghost army, there'd be no reason not to add a general and heroes into the mix.
Never having played with these units, how do they compare to the other Warmaster armies? Would 1000 points of Ethereal Host be stronger or weaker than a typical army? If stronger or weaker, how much would you need to adjust the total points of each army to give a balanced game?
Has anyone ever looked at an army composed of a single unit type such as this?
