When The Fugitive Doctor enters, investigate.
Whenever The Fugitive Doctor attacks, you may sacrifice a Clue. When you do, target instant or sorcery card in your graveyard gains flashback 
until end of turn. (You may cast that card from your graveyard for its flashback cost. Then exile it.)
Illustrated by Greg Staples · Doctor Who · #417
2023-10-13
"Investigate" means "Create a Clue token." A Clue token is a colorless Clue artifact token with "{2}, Sacrifice this artifact: Draw a card."
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"Flashback [cost]" means "You may cast this card from your graveyard by paying [cost] rather than paying its mana cost" and "If the flashback cost was paid, exile this card instead of putting it anywhere else any time it would leave the stack."
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You must still follow any timing restrictions and permissions, including those based on the card's type. For instance, you can cast a sorcery using flashback only when you could normally cast a sorcery.
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To determine the total cost of a spell, start with the mana cost or alternative cost (such as a flashback cost) you're paying, add any cost increases, then apply any cost reductions. The mana value of the spell is determined only by its mana cost, no matter what the total cost to cast the spell was.
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A spell cast using flashback will always be exiled afterward, whether it resolves, is countered, or leaves the stack in some other way.
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If you cast an instant or sorcery with {X} in its mana cost this way, you must choose 0 as the value of X. (You still have to pay {2}{R}{G}.)
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If a card has multiple instances of flashback, you may choose any of its flashback costs to pay.
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If a split card gains flashback, you pay only the cost of the half you're casting.
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Unlike other creature types in Magic that are each only one word, the two words "Time Lord" represent a single creature subtype. Time Lord is the only two-word creature type.
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Neither "Time" nor "Lord" are creature types. Some older cards were printed with the subtype "Lord," but all of those cards have updated Oracle card text that removed that type.
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If an effect instructs you to choose a creature type, you may choose Time Lord.
: Time travel three times. Activate only as a sorcery. (For each suspended card you own and each permanent you control with a time counter on it, you may add or remove a time counter. Then do it two more times.)
, Sacrifice this token: You gain 3 life.")
