Shuffle your whammy deck, then reveal cards from the top of your whammy deck until you reveal an Island or choose to stop. Then, if no Islands were revealed this way, Whammy Burn deals X damage to any target, where X is the number of cards revealed. (A whammy deck consists of a Plains, Island, Swamp, Mountain, and Forest.)
You choose a target as you cast Whammy Burn, before revealing any cards from your whammy deck.
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wotc
You can’t draw cards from the whammy deck or interact with it in any way other than by effects that specifically interact with the whammy deck. Effects that affect cards you own not on the battlefield don’t affect cards in the whammy deck.
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wotc
The whammy deck exists in the additional deck zone. Since this is a game zone, it’s not outside the game (for effects such as that of Frontier Explorer).
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wotc
If you don’t have a whammy deck when an effect refers to it, shuffle a Plains, Island, Swamp, Mountain, and Forest card from outside the game to form your whammy deck immediately before performing any part of that effect.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.