Earth Elementals are living mass of earth and stone. Their physical form gives them natural resistance to mundane weapons and they are completely immune to acid.
Summon - Unit was summoned and belongs to another world.
Acid Immunity - Unit is immune to Acid damage.
Elemental - Unit is immune to Mind-affecting effects, Critical hits, poison and sneak attacks.
Illusion Immunity - Unit is immune to illusions. It can see invisible units and illusory attacks do not ignore its armor.
Mundane Resistance - Unit receives 10 less damage from all Mundane attacks.