To halve the damage when being attacked, regardless of the unit the whole with a 50% probability. In the damage caused by the "poison" and "freezing" does not activate. Damage is not decreased to activate special abilities.
Alone, when attacked both whole and halved the damage caused by a probability of 50%. Effect can not be triggered by damage caused by the "poison", "frozen". It does not reduce damage when you activate a special ability.
When attacked, regardless of the damage to the entire half of 50% probability. At the "poison" freeze "damage" by the effect of the engine. Don't damage can be reduced when the special ability.