You can learn more about everything included in boosters with Product Architect Mike Turian's Collecting Innistrad: Crimson Vow article, and be sure to see all the delightful card frames themselves in Clayton Kroh's Booster Fun article
The pull odds tell the story: one Master Ball mirror per box, 153 possible cards, meaning you need roughly 153 boxes (~6.3 million / ~$43,000) to statistically expect one Gengar
Our complete series of Kaladesh Spoilers for Magic: the Gathering will give you a complete run down on every single spoiler card revealed over the pre-release spoiler season
Drop the Abzan Banner , Ghalta, Primal Hunger , Crashing Drawbridge , Llanowar Elves , Quarry Hauler , Quirion Elves , Rampaging Baloths , Rubblehulk , Sporecrown Thallid , Volcanic Geyser , Rampant Growth , Strength of the Pack , Farseek and Life and Limb
Do note, however, that the card names here arent always final