Bandai has published the detailed rule explanation on April 23, which happens to debunk many of the earlier rulings. This is an especially important ruling update and Bandai highly recommends that players read and understand the new rulings.
Note that certain older rules (including the ones we published earlier) are now defunct. We will convey the changes in an upcoming post so please stay tuned.
The source documents are currently only available in Japanese. You can read them here.
Activation, Pending Resolution, and Resolution of effects
While we await the official English text for keywords, we will use the following English translations.
Some of the effects of Digimon and Tamers are [On Play], [When Digivolving], [When Deleted], [When Attacking], and " when XX" will only be exhibited when specific timings and conditions are met.
When the conditions for these effects are met and the effect can be resolved, it is called "activate/trigger".
And when the effect is actually applied, it is called "resolve".
The activated/triggered effect is basically resolved immediately and the effect is applied, but when multiple effects are activated/triggered at the same time, depending on the order in which the effects are resolved, there may be a gap between the trigger and the resolution.
The period from this trigger to the resolution is called "pending resolve".
Prior to resolution, if the Digimon or Tamer whose effects are pending resolution are no longer there, then that effect will not resolve.
The difference between Past and Present tenses
When you use/… (past)
When using/… (present)
In the text of the effect, there are effects that trigger "when you play/use/digivolve/…" (past tense) and effects that trigger "when you are playing/using/digivolving/…" (present tense).
There is a difference between the two.
Past tense effects are triggered after the condition has occured.
Example: "When this Digimon is deleted" triggers when your Digimon disappears (see [BT2-073] Garurumon as an example).
Present tense effects are triggered right before the condition is about to occur.
Example: "When this Digimon would be deleted" triggers when your Digimon is in a state of deletion, before it is actually deleted (see [BT2-082] Diaboromon as an example).
Present tense effects are resolved by interrupting the action that became the condition. Depending on the effect, the conditional action itself may be cancelled.
Example: If the effect is "When your Digimon would be deleted, return that Digimon to your hand" will return your Digimon to your hand before it actually disappears.
Regarding effects that resolve in trash
Digimon and Tamer effects are often only available when you are in the battle area. However, some effects, such as [On Deletion] effects, are resolved when placed in the trash.
When placed in the trash, the digivolution source card is no longer the digivolution source, but when it resolves the effect at the time of [On Deletion], it will be effective as it is still in the state of deletion (not actually deleted yet).
Example: When your "Greymon" is deleted while having a digivolution card with the digivolution source effect "[On Deletion] When this Digimon has "Greymon" in its name …", the effect will trigger and resolve.
If a card is pending resolution of its [On Deletion] effect is moved from the trash to your hand or deck, or appears in the battle area or raising area and disappears from the trash, then the source of the effect has disappeared hence the effect will fail to resolve.
Also, in the case of the digivolution source's [On Deletion] effect, even if the (digivolution) card itself with the effect remains in the trash, while the Digimon card that was stacked on top at the time of [On Deletion] disappears from the trash, the effect cannot be resolved.
Example: When your "Greymon" is deleted while having an "Agumon" as its digivolution card, and "Agumon" has a digivolution source effect that triggers [On Deletion]. During the pending resolution phase of "Agumon's" [On Deletion] source effect, the corresponding "Greymon" was returned from the trash to your hand, then "Agumon's" [On Deletion] source effect will fail to resolve.
Regarding blanket effects
Some effects, such as "for the turn" and "until the end of your opponent's next turn," will continue for a while from the moment they are resolved.
Basically, these effects are only applicable to the cards that are in the battle area at the moment that they are resolved. However, effects that target "All Digimons", "All your Digimon", and "All your opponent's Digimon" etc. will be applied to Digimons that appear both before and after the effect is resolved, including Digimons that moved from the breeding area to the battle area.
When multiple effects that has already been resolved overlaps
If multiple blanket effects overlap, all of those effects will be applied to Digimon newly entering the battle area at the same time.
If the positive and negative effects such as DP+ and DP- are applied at the same time, the positive and negative values are deducted in advance and then the difference is applied.
Example: If the effect of DP +3000 and the effect of DP -5000 are applied at the same time, the effect of DP -2000 will be applied by deduction.
If a LV2 Digimon appears in the battle area
Depending on the combination of several effects, a LV2 or lower Digimon may appear in the battle area.
In that case, since the LV2 or lower Digimon cannot exist in the battle area, it will be trashed. This is not treated as a deletion.
If the DP of a Digimon becomes 0
Digimon's DP does not decrease even if it is attacked, but can be temporarily decreased due to the effect of DP reduction.
If such an effect causes a Digimon's DP to become 0 (it cannot be less than 0), that Digimon will be deleted and trashed.
Even if a Digimon's DP becomes 0 due to the effect of DP reduction, it is deleted according to the rules. However, this is not considered to be deleted by card effect.
If the DP of a Digimon becomes 0 at the same time as it is played or moved from the raising area
Due to blanket effects, it is possible for a Digimon to have a DP of 0 at the same time as they were played.
In this case, since the Digimon is deleted before it's [On Play] effect is resolved, that Digimon's [On Play] effect cannot be resolved.
However, since the condition "when a Digimon is played" is satisfied, therefore any effects that contain "when your Digimon is played" or "when your opponent's Digimon is played" from any other Digimon will still be resolved.
Regarding [Start of Your Turn] and At End of Turn effects
Start of Your Turn
At End of Turn
The [Start of Your Turn] effect is resolved at the beginning of your turn, before the unsuspend phase.
If there are multiple [Start of Your Turn] effects, the card's player will decide the order in which they resolve.
The "At End of Turn" effect is resolved when the memory is moved to 1 or more at the opponent's side, and the conditions for passing turns are met. The turn will not pass until all of these effects are resolved.
However, if the memory becomes 0 or more (at your side) due to effects, then the turn will not pass and your turn will continue. In this case, the "At End of Turn" effect may be used more than once.
Regarding [When Attacking] effects
The effects of [When Attacking] and "when your Digimon attacks" will activate/trigger when your Digimon declares an attack.
After the attack declaration, if the attacking Digimon changes into another Digimon (due to digivolution or de-dedigivolution) and as a result acquires a new [When Attacking] effect, that new effect is not resolved because it does not exist during the attack declaration.
The effect of "when your opponent's Digimon attacks" is activated/triggered at the "Reaction" timing.
Reaction is the timing after your opponent's Digimon attacks and all the effects of [When Attacking] and "when your Digimon attacks" has been resolved.
[When Attacking] effects will not activate/trigger unless it exists at the time of attack declaration, but even if the effect of "when your opponent's Digimon attacks" does not exist at the time of the attack declaration, if the effect is acquired before the reaction then it can be triggered and resolved at the time of reaction.
Regarding multiple target effects.
When selecting multiple targets, there is a difference between selecting "N cards" and "up to N cards".
In the case of selecting "N cards", it is necessary to select as many targets as possible.
Example: If the effect is "3 of your opponent's LV3 Digimon", you must select 3 of your opponent's LV3 Digimon. If your opponent only has 2 LV3 Digimons then you must choose as many as possible, which is all 2 Digimons.
In the case of "up to N cards", you can select any number of targets between 1 and the specified number N (you must select at least 1 target if there is at least one Digimon or Tamer that can be targeted).
Example: If the effect is "up to 3 of your opponent's LV3 Digimon" then you may select any number of your opponent's LV3 Digimon from a range of 1 to 3.
Regarding By Doing effects
By doing M, do N
Some effect texts have a format of "by doing M, do N".
For this type of effect, you can apply the "N" portion of the effect by executing the "M" portion first. If you do not wish to resolve the effect, you may choose not to perform the earlier "M" portion. For effects with a limited use times, such as [Once Per Turn] effects, the number-of-times is not consumed if you choose not to perform the "M" portion.
In addition, it is possible to execute "by doing M" even when executing the subsequent "N" portion is not possible. In such cases, the number-of-times limit such as [Once Per Turn] is consumed by the effect.
Example: The effect "by trashing one card from the top of your security stack, one of your opponent's Digimon gets -2000 DP for the turn" can be activated even when your opponent does not have a Digimon in the battle area. However, if your security is at 0 cards then you are unable to perform the "by trashing one card from the top of your security" portion hence you cannot activate this effect.
Regarding effects separated by then
Some effect texts have a format in which the front and back portions are separated by the word "then", such as "do M. Then, do N".
For these effects, first perform the aforementioned "M" and then followed by the "N" portion described later.
This effect will be resolved even when you are unable to perform either or both of "M" and "N".
If an object meets the conditions of "M" by "N", it will be affected by "M".
Example: Based on the effect of "trash the digivolution card at the bottom of all your opponent's Digimon. Then, gain +1 memory for each of your opponent's Digimon that does not have a digivolution card.", your opponent's Digimons that loses their digivolution cards as a result of this effect, will also count towards the latter part of this effect, allowing you to gain +1 memory for each of them that no longer has any digivolution cards.
In addition, although there is an order of "M" → "N", but the effects triggered as a result of either "M" or "N" are treated as if they were triggered at the same time.
Example: For the effect "Trash 1 card from the top of both players' security stacks. Then, play 1 purple or yellow Digimon card with a level of 4 or less from your trash without paying its memory cost.", the "when your security is reduced" effect triggered by the first half and the "[On Play] effect of the revived Digimon" triggered in the second half are both considered to be triggered at the same time, and the order can be determined by the owner of that card.
Regarding the use and target of option cards
Option cards can be used even when there are no cards such as Digimon or Tamers that can be the target of that card, as long as the option card's memory cost can be paid. The option card used in this way has basically no effect, but the "when you use an option card" effect of other cards can be resolved.
On the contrary, option cards cannot be used without selecting a target when a target exists. At least one target must be selected for "up to N cards" effects, and as many as possible selected for "N cards" effects (see the "Regarding multiple target effects" section).