Once you've announced that you're casting this spell, players can't take any actions until you've finished doing so
If you discard a card after all three have been chosen in a turn, that instance of the ability is removed from the stack with no effect
Every time some kind of Magic: The Gathering Secret Lair deck gets shipped, Wizards of the Coast seems to accidentally send an unrevealed product to a select few customers, resulting in leaks
It's also a card I expect to be cheap for a while, which guarantees that I'll be running it at least as a budget option for Green Self-Mill decks
In a normal 60 card format, even as a 40/40, its killing anyone without regard to life gain in a single hit
If you cast a spell with its escape permission, you can't choose to apply any other alternative costs or to cast it without paying its mana cost