The basic is the more Trainer Cards your opponent's Hand has, the higher the Damage from Gengar & Mimikyu GX's Attack Poltergeist. The Attack does 50 Damage for each Trainer Card in your opponent's Hand. So, our goal here is to either increase Trainer Card in your opponent's Hand or prevent your opponent's from using Trainer Cards.
If you have 1 Extra Psychic Energy Attach to Gengar & Mimikyu GX, its GX Attack Horror House not only prevent your opponent from playing cards from his or her Hand, also let your opponent draw until he or she has 7 Cards in Hand. This effect is the perfect combo for Poltergeist Attack.
Full Article at https://ptcg92.blogspot.com/2019/09/gengar-mimiikyu-team-up.html
