I have seen treasure cards have been an ingredients for houses, and other rare items. Do you actually have to have that spell in your spell deck, or is it actually for reagents??
the treasure cards you use for these are the ones you can buy from the library, bazaar, archivist, or that you get from creature drops, treasure chests, certain plants through gardening. there are also some treasure cards you can craft with the recipe from your school's tree. however, you can't use a treasure card that you make by putting a tough or accuracy treasure card spell on. make sure the treasure card you get matches the card in the recipe exactly. good luck, and i hope this helps. -eli and crew