Why do all my cards have a red border? [Have gold, have available pop]

[odin87654321]

I can't play any of the cards in my hand, and I don't know why. I have 150+ gold, and 16/29 ratizens. I can't play a Caravan Guard (57 gold, 1 ratizen) or a Merc (40 gold, no ratizen) or a single Cheese (40 gold, no ratizen). I am at wave 13. Very confused.

[Fel]

You are mistaken about what red border means I think.

Green border means that you can play that card, no border means that you can't afford it and red border is for discard/remove.

Since you are playing the merchant leader, you most likely played a card that asks you to discard 1 or more cards so all cards will have that red border until you do that.

You should first make sure what the card you played is asking you to do because there is a big difference between sending a card to the discard pile (or graveyard as it is called in many card games) and removing a card from your deck.
Most of the removal from card effects are from the navigator but it doesn't hurt to double check.

[odin87654321]

Well I'm definitely mistaken about something! Thank you, I'll try and watch that more carefully to see if that is what is happening.