Umbreon V [Brilliant Stars] While Umbreon V is mostly prized for its card art (Moonbreon especially), the Brilliant Stars Trainer Gallery is also worth considering
It finds the cards you need, protects the card you cannot afford to lose, and helps the archetype feel less like a nostalgic gimmick and more like a real strategy
For players, these packs provide opportunities to discover powerful Pokmon ex cards and valuable Trainer cards that can strengthen competitive decks
When your creatures die, or even possibly an opponents creatures, you cause each or target player to lose life while you gain life
Many of your decks run Nikya of the Old Ways and thus aren't running many (or any) non-creature answers
Even if it is removed, after reviving and returning "Dragon God Grapha of the Dark World" due to the effect of (2), the effect of discarding cards from each other's hand is also compatible with the "Dark World" Deck, so I think there is no waste