So, let's go over perhaps the most important part: finding a place to play a Prerelease
Without dual lands it would be near impossible to construct competitive two or more colour decks and the result would be a very boring and narrow meta game
ALL the character, and all cards underneath it go to the inkwell
Remember, these cards care about how much mana you actually spent on the spell, not the printed mana value so the higher tiers of Ice Magic and Thunder Magic, the flashback casts of Dreams of Laguna and Laughing Mad, and a big Syncopate or Choco-Comet will all work to trigger your stuff
For the ETB effect, we borrowed an effect that premiered on We wanted the back face to be protective in flavor, but we didn't want it stalling out games, so we needed to give it an aggressive element