Giant Sighting allowed players to pay one shoot card as a Challenge per turn. It kept coming up for new players though and really confusing them, as well as it would last forever because no one would use it.
Most of the "this card can be played as another card" effects had been removed already as well. Besides capture spell card and Satori which are staying I think they're all gone.
Given this knowledge, why not phrase the card like this?
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Giant Sighting
Once on each player's turn, they may choose another player. If they do, starting with the chosen player, both players take turns discarding Danmaku cards until one player passes. That player loses 1 life, while the other player draws 2 cards.
Collect the top card of the deck during each player's incident step. Collect any Danmaku cards.
Resolution: Collect 15 cards.
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Essentially, I just removed the cost and replaced it with a "once per turn" mechanic, so that it doesn't go through the whole "treat one card like it's something else" sort of thing, but is essentially a "Challenge one player for free, and receive a reward if you win" sort of incident, which will lead people to want to use said effect for a chance at drawing cards. A high risk, high reward sort of card, if you would.
I also set a sort of time limit to the card, much in the same vein as the Eternal Night incident card, so that if no one uses it for some reason, then it won't linger for too long. It still takes 15 cards to resolve it, though, so that if people do use it, then it can be used a few times before fizzling out.
What do you think about said adjustment to the card?