There are 4 Ultra-Rare cards; X-Ray, The Sandstone City, Angkor and Easter Island Stronghold. Each unlocks a clue on it's own. They are available in Card Packs 1, 2, 3, and 4 respectively, but the first 3 are available in Card Pack 4.
Pages in category "Ultra-Rare Cards"
“ Every clue has a card combo and every card combo has a Clue Key. Here are the clue keys (in...