- Does Gengar & Mimikyu GX's "Horror House GX" attack prevent me from using Viridian Forest?
- No, it does not. Discarding a card from your hand is not the same as playing a card from your hand; the card goes to the discard pile, not "in play".
Source:
TPCi Rules Team (2019-08-22)
Relevant cards
Note: All applicable cards may not be listed below.
SM9_156
SM9_164
SM9_165
SM9_186
SM9_53