If I have Eternatus VMAX with the "Eternal Zone" Ability in play, can my opponent use Mawile GX's "Captivating Wink" Ability to play any non-Darkness Pokémon onto my bench?
No, if Eternal Zone is working, your opponent cannot force you to put any non-Darkness Pokémon into play.
Source: TPCi Rules Team (2020-09-24)
If my already-poisoned Pokemon is hit by Dragalge's "Poison Cultivation" attack then I use Switch while Dust Island is in play, is my new Active Pokemon poisoned with a regular condition (only one damage counter in between turns) or with the effect from "Poison Cultivation" (ten damage counters in between turns)?
If the Poison effect places more than one damage counter during the Pokémon Checkup phase between turns, then switching the Pokémon out using a Trainer card while Dust Island is in play will retain the modified Poison effect of placing multiple damage counters on the new Active Pokémon.
Source: TPCi Rules Team (2020-09-24)
I know using Darkrai {*}'s "Nightmare Star" Ability is optional, but can I choose to attach only one Darkness Energy card if I have two in my hand?
Since the contents of the hand is not public knowledge, you may attach only one if you wish.
Source: TPCi Rules Team (2020-09-17)
If my only Eternatus VMAX with "Eternal Zone" Ability is Active and gets KO'd, do I reduce my bench size down to 5 Pokemon before or after promoting one to the Active Slot?
You discard down to 5 Benched Pokemon before promoting a new Active Pokemon in this scenario.
Source: TPCi Rules Team (2020-08-20)
If I use Devolution Spray Z to devolve Eternatus VMAX with "Eternal Zone" Ability with enough damage already on the devolved Eternatus V to knock it out, is it KO'd before having to reduce my Bench down to 5 Pokemon, or if I discard it to reduce my bench is it not KO'd?
Well if the Eternatus VMAX is active it would get KO'd after reducing the Bench, but if the devolved Eternatus V is on the bench you could discard it as part of the bench reduction to avoid a KO.
Source: TPCi Rules Team (2020-08-20)
If I have Eternatus VMAX with "Eternal Zone" Ability in play and I use Devolution Spray Z to devolve one of my benched Darkness type Pokemon to a non-Darkness type Pokemon with enough damage already on the devolved Pokemon to knock it out, is it KO'd before having to reduce my Bench down to 5 Pokemon, or if I discard it to reduce my bench is it not KO'd?
You would discard your Bench down to 5 first, then check for a KO. That means you could discard the newly devolved Pokemon to avoid a KO, even if Eternatus VMAX is the one being devolved!
Source: TPCi Rules Team (2020-08-13)
What happens if I play Bird Keeper but there aren't any Pokemon on my bench?
If you only have one Pokemon in play, you cannot play Bird Keeper.
Source: Darkness Ablaze FAQ (2020-07-31), TPCi Rules Team (2020-08-13)
How does Billowing Smoke work with Greedy Dice or Jirachi {*} and its "Wish Upon a Star" Ability?
If you KO a Pokemon with Billowing Smoke attached, you do not get to use Greedy Dice nor Wish Upon a Star since neither of those cards would be going into your hand. Any Prize cards that would be taken for a Pokemon that has Billowing Smoke attached are discarded, not taken.
Source: Darkness Ablaze FAQ (2020-07-31), TPCi Rules Team (2020-08-13)
Does Galar Mine add {*}{*} to the Retreat Cost of a Darkness Pokemon with Hiding Energy attached?
Nope, if a Pokemon's Retreat Cost is set to zero by an effect such as Hiding Energy, it cannot be increased by Galar Mine.
Source: Darkness Ablaze FAQ (2020-07-31), TPCi Rules Team (2020-08-13)