Lucky X: A cumulative, static ability that means, "Each time this unit attacks or is attacked, you may re-roll up to X of this unit's attack dice or have your opponent re-roll up to X attack dice against this unit." Both players can use Lucky effects according to the rules for POP chances. Lucky is used only once after all triggered re-roll effects resolve. You can't re-roll more dice than are rolled for the attack. You may choose to roll any number of dice up to the Lucky value.
Parry
Parry X: A cumulative ability triggered during the damage prevention POP that means, "If the attacking unit rolled at least one natural '1' against this unit, prevent X damage to this unit." Only one natural "1" is counted from the attack roll after re-rolls. Parry doesn't prevent damage from a parrying unit unless it attacks itself. Parry can't affect unpreventable damage. If a unit gets the Parry ability after you roll attack dice, it's too late to affect the damage. Accuracy can't decrease the die roll to a natural "1". However, you or your opponent may use an effect to re-roll dice to affect the number of natural ones. (You only count the 1, if any, from the roll used for the attack.) Parry applies only to dice rolled for an attack, not to dice rolls for abilities like Retaliate.
Shields
Shields X: A cumulative, static ability that means, "The attacking unit gets –X power against this unit." Shields only matters when attack dice are rolled. If you give a unit Shields after your opponent has rolled for damage, it doesn't affect the roll.
Stun
Stun X: A cumulative ability triggered during the damage placement POP that means, "When this unit damages another unit, that unit gets –X power until end of battle." If no damage counters are placed as a result of damage, Stun doesn't occur. Stun works anytime the unit damages another unit, not just when it attacks. Only the unit with both Deflect and Stun abilities can stun when it activates its Deflect.