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Flying
At the beginning of your upkeep, mill a card. If an instant or sorcery card was milled this way, transform this creature. (To mill a card, put the top card of your library into your graveyard.)
If a replacement effect causes the top card of your library to go to a zone other than your graveyard, Aberrant Researcher will still transform if that card was an instant or sorcery card.
No player may take any action between the two steps of Aberrant Researcher's triggered ability. If the card put into your graveyard is an instant or sorcery card, Aberrant Researcher will have transformed before a player can take any action.
