Speak up in the next 24 hours or so if you spot any game-breaking bugs!
Great cards! I didn't find anything I'd consider game-breaking, but I did go overthem with a "fine-toothed comb" and found the following typos, wording improvement suggestions:
Discovery - "When you flip this face-up" There is no mention of ever putting the card face down. Is that somewhere in additional rules? I'm not sure whether it should be put in the card text itself.
Gamepiece – Possible wording improvement: "When you discard this on your turn, and not during Clean-up"
Inspector – For accountability the other players need to reveal the card from their hand before putting it on their deck. (See Bureaucrat: "Each other player reveals a Victory card from their hand and puts it onto their deck (or reveals a hand with no Victory cards).") The word reveal also makes it more clear that the card is coming from their hand. Also, instead of using "copy of that card", I'd suggest using "matches". (See Doctor: "Name a card. Reveal the top 3 cards of your deck. Trash the matches.")
Suggested text: "Reveal 2 cards from your hand, then discard them. Each other player with 4 or more cards in hand reveals one that matches one of your revealed cards and puts it onto their deck (or reveals they can't)."
Moundbuilder Village - Since all cards in play can be discarded at once, I think this means you can set aside a card that was just played this turn and during Clean-up was discarded at the same time as Moundbuilder Village. This may be a point to make in any additional printed rules/explanation for the card.
Profiteer - The phrase "cards in your hand and deck cost 0 or 1 more" might be more clear if you add the word "all" before "cards".
Riches - The period should be placed outside the final parenthesis "(including other Riches)."
Shipwreck - Incorrect word order in last sentence. Should be "When you buy
this for 4…"
Stronghold - The text is missing a word. It should say: "return
to your Action phase first."
Tomb Raider - The period should be placed outside the final parenthesis "(or reveals they can't)."