Phantom Warriors are illusions. Their attacks are a matter of arcane power, not physical force and can pierce any armor. They are, however, very fragile.
Summon - Unit was summoned and belongs to another world.
Construct - Unit is immune to Mind and Death effects, poison, critical hits, Gaze attacks and Positive and Negative energy. They cannot be raised from the dead.
Ethereal - Unit's attacks ignore armor (are more likely to hit).