[Endoperez]

The AoE or Area of Effect means that the spell affects one grid (press 'g' in the battle), each holding up to three size 2 unit, two size 3 units or any other combination of units, whose summed sizes do not exceed 6. The mage might cast it on himself before the soldiers, so either multiple mages or few turns' time are needed to be sure of it.

IIRC, Broken Empire Ermor starts with Body Ethereal... They don't have cheap astral mages, but it is the easiest way to try things out.