There are creatures whose physical bodies have long since rotted away, if indeed they ever existed. Such beings are immune to normal weapons – only magic can harm them.
Ethereal creatures treat all terrain as open terrain for the purposes of movement. They may not finish their movement inside impassable terrain. They are also never slowed by any special rule, spell or item that would otherwise reduce their movement or stop them from moving completely.
Models with this special rule have both theand special rules. Ethereal models can only be wounded by spells, magical attacks and magic weapons or effects. Ethereal creatures block line of sight normally and cannot see through anything that would block the line of sight of normal units. Characters that are not themselves Ethereal are not permitted to join units that are (even if they become temporarily Ethereal for some reason).