Ethereal

The model can only be harmed by magical attacks, spells, Flaming Attacks or other Ethereal models -- any other attack that would hit it simply has no effect. It has a Ward save (4+), or its own Ward save if better. It treats all terrain as open ground (never taking Dangerous Terrain tests) and may move through and finish a move on top of impassable terrain or other models, friend or foe.