Critical Hit X: A cumulative ability triggered during the pending damage POP that means, "If you rolled at least one natural six with this unit's attack dice, this unit does X more damage for this attack." Only one natural "6" counts in the attack roll after re-rolls. If a unit gets the Critical Hit ability after you roll attack dice, it's too late to affect the damage. Accuracy can't increase the die roll to a natural "6". However, you or your opponent may use an effect to re-roll dice to affect the number of natural sixes. (You only count the six, if any, from the roll used for the attack.) Critical Hit applies only to dice rolled for an attack, not to dice rolls for abilities like Retaliate.
INSERT
INSERT: A layered, static ability that means, "When this card is in play or stacked under the unit, the unit gets the following effect:" Insert works while in the build zone. The effect works while anywhere in the unit's stack. The granted ability remains to be the ability of its type. (For example, activated abilities granted by Insert may be disrupted.) The granted effect may not work in the build zone as per the rule for the rule for that effect.
Protect
Protect X: A layered ability activated during the damage prevention POP that means, "Prevent up to X damage to one of your other units in this arena." You can play Protect only once for each instance of damage. You don't have to use all of the Protect. You choose how much damage to Protect up to X, even if the full amount of damage or more is pending.
Riposte
Riposte X: A cumulative ability triggered by the roll of a natural two during an attack that means, "If the attacking unit rolled at least one natural two against this unit, this unit does X damage to it when the attack ends." Only one natural "2" is counted from the attack roll after re-rolls. Negative Accuracy can't decrease the die roll to a natural "2". However, you or your opponent may use an effect to re-roll dice to affect the number of natural twos. (You only count the 2, if any, from the roll used for the attack.) Riposte applies only to dice rolled for an attack, not to dice rolls for abilities like Retaliate.