A recent ruling confusion has caused a heated debate on the Facebook Digimon Card Game TCG community.
The post on April 10 started with a ruling clarification that if you de-digivolve a <Blocker> Digimon on attack declaration and that blocker no longer has the keyword <Blocker>, is still able to block the attack because it was a blocker on declaration. This statement then went to pull more than 200 comments, with a variety of scenarios raised.
Today we will try to debunk this confusing mechanic by using a more visual method.
Game attack mechanics
We also know that blocker Digimons will activate <Blocker> in the same timing window , which is remarked in Bandai's reply for this related mechanic (see later in this post).
Here, the term activated does not mean resolved. Generally, effect timing can be split into 2: activate and resolve.
Activation of an effect simply lights it up! Nothing actually happens but you can imagine that the effect is being queued up in some effect queue.
Resolution of effects meanwhile, resolves effects in the order that they were queued. Things happen when effects are resolved (cards are drawn, or Digimons are deleted etc.) and may impact subsequent effects downstream in the queue.
While not officially described in the rulebook, Bandai has been very consistent with the terms activate and resolve (see some sample replied from Bandai in the later parts of this post).
Due to this activate/resolve phases, the <Blocker> effect will always activate behind-the-scenes (the player does not need to explicitly say to block). This is because nothing actually happens when you trigger or activate the <Blocker> effect, and the actual blocking (or even decision whether or not to block) happens during resolution.
<Blocker> (When an opponent's Digimon attacks, you may suspend this Digimon to force the opponent to attack it instead)
Note that when  resolving the effects of a blocker, the player MAY SUSPEND his Digimon in order to block. Therefore, decision to block is made during timing window  and not in . This is also consistent with page 6 of Bandai's Q&A General Rules.
To make this more intuitive, we can visualize this entire mechanism as a effect queue.
When effects are activated, they are queued into an imaginary effect queue. Although both [When Attacking] effects and <Blocker> effects have the same activation timing, the queued effects are resolved based on turn-player priority.
After all the  activations, the  resolution phase will simply resolve effects from the queue in order of turn-player priority.
Scenario 1: blocking Crusadermon
Q: You attack your opponent with [BT5-045] Crusadermon and using his [When Attacking] effect, you play a [BT5-042] Knightmon from your hand. Can you destroy your opponent's blocker using Knightmon's [When Played] effect, rendering that blocker unable to block Crusadermon's attack?
A: No. Your opponent can resolve the blocker's effect before your Knightmon's [When Played] effect. Therefore, your opponent's blocker will be able to block your Crusadermon.
This question has been officially confirmed by Bandai/Cardass. The blocker Digimon has a queue priority before Knightmon's [When Played] effect hence is able to block Crusadermon.
Crusadermon must resolve all [When Attacking] effects first before the blocker, and the blocker Digimon can decide whether on not to block the attack depending on how the situation plays out.
Also note that since Knightmon's [When Played] effect resolve after the blocker, therefore he can choose his target after observing whether the blocker Digimon decides to block or not.
Scenario 2: blocking De-Digivolution
Q: You attack your opponent with a Digimon that has the effect [When Attacking] Trigger <De-Digivolve 1> on 1 of your opponent's Digimon. You target that <De-Digivolve 1> effect on 1 of your opponent's blocker Digimon, causing it to de-digivolve into a Digimon that no longer has the keyword <Blocker>. Can that de-digivolved Digimon block the attack?
A: Yes, because the <Blocker> effect is activated before the <De-Digivolution 1> effect is resolved. By the description of <Blocker> (When an opponent's Digimon attacks, you may suspend this Digimon to force the opponent to attack it instead), your de-digivolved Digimon will be able to block the attack as long as it is able to suspend itself.
This was also debated on Facebook back in April 4, and has been confirmed with Bandai/Cardass.
The sequence of events in this scenario conforms to the same activate/resolve mechanic: the effect has been activated and queued prior to resolving the effect. Therefore, the effect will still resolve as per its description: when an opponent's Digimon attacks, you may suspend this Digimon to force the opponent to attack it instead.
Card game mechanics can be rather confusing when not properly documented, but it is important to play by the official rules to avoid disputes in the middle of a game. Do let us know if there are certain rulings you wish clarified and we shall do our best to help!
Many thanks to our dear friend Samuel (Deuk-Boo Jang) for helping to review the rulings mentioned in this post.