Treasure Trove includes more souvenir cards to shuffle into the souvenir deck, legendary artifact cards for you to discover, and injury cards which give you a choice to take a random disadvantage rather than give up a treasure when hit by a fireball.
These cards won't be in the retail game which is what is being shipped to backers so they will come as an extra package. The publisher has said that they will be selling it only through their web store, conventions, and maybe the BGG store.
This expansion to Fireball Island: The Curse of Vul-Kar is a collection of cards unlocked via stretch goals during the Kickstarter campaign.
Contents:
Hangry (12 souvenirs that ramp up the meanness to 11!)
Injuries (12 cards you can take instead of losing a treasure)
Legendary Artifacts (6 super-powerful souvenirs)
Bonus Souvenirs (18 new souvenirs to add to your regular deck)
3 Blank souvenir and 2 blank injury cards so you can make your own designs