(2022-04-29) Casualty N means As an additional cost to cast this spell, you may sacrifice a creature with power N or greater. and When you cast this spell, if a casualty cost was paid for it, copy it
The adventure mechanic was a direct response to an issue Set Design came up against: they felt that Vision Designs set was too focused on making big mechanical choices during deck building and not enough during play (Set Design lead Mark Gotlieb has written a full account of how Adventures were designed)
More mana means you can play bigger spells like Etali, Primal Conqueror or have a bigger value for X like with Zoanthrope
How Do Learn Cards Work in Sealed Deck and Booster Draft Events
Your goal is to buy sleeves that age predictably, don't split early, and keep a consistent shuffle feel
Moxen are jewelry and the cards are very iconic looking for this reason