Inexorable Storm

Return all nonland permanents to their owners'
hands. Until your next turn, each player's
maximum hand size is reduced by four.
At the beginning of your next end step, if seven
or more permanents were returned to their
owners' hands this turn, exile Inexorable Storm
from your graveyard and return it to the
battlefield transformed.
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https://mtgcardsmith.com/view/after-the-storm-2