So if I have a -1 Card token on my deck and play a Mystic, it'll reveal that -1 Card token, or the card under it? If it's the latter, that means it removes the token instead of drawing a correctly guessed card?
The -1 Card token does not affect Mystic at all. The token stays on your deck regardless of whether you guessed right.
The -1 Card token only affects three things:
- When a card says +X Cards
- When a card uses the word "draw" (except Envoy, which shouldn't use "draw" but does)
- When you draw your new hand at the end of a turn
Everything else skips past the token and the token stays on your deck.
So for instance, let's say your token is on your deck and you play Catacombs.
You still look at 3 cards. If you choose to put them into your hand, then that's the end and the token stays. If you discard them and get +3 Cards, you'd remove the token and draw 2 cards.