The adventure portion, "Granted," allows you to find a card you own from outside of the game (usually your sideboard) and put it into your hand
If you control 12 or more "decorated" cards at the start of your upkeep, you automatically win the game
Mystic Snake was often a way to do damage to an opponent who you otherwise couldn't find an opening to get a threat down against or a two-for-one by fighting one of the many bears that were in decks in those days, and when it did these things it was good
These decks should generally not have any two-card infinite combos that can happen cheaply and in about the first six or so turns of the game, but it's possible the long game could end with one being deployed, even out of nowhere
And then, you draw the same number of cards as their opponent shuffled
That's right, any time a source of damage is dealt to you or a permanent you control, the controller loses two life unless they pay one mana