Memory's Journey — ruling 1

If a card with flashback is put into your graveyard during your turn, you can cast it if it's legal to do so before any other player can take any actions.

Memory's Journey — ruling 2

"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."

Memory's Journey — ruling 3

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.

Memory's Journey — ruling 4

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.

Memory's Journey — ruling 5

A spell cast using flashback will always be exiled afterward, whether it resolves, is countered, or leaves the stack in some other way.

Memory's Journey — ruling 6

You can cast a spell using flashback even if it was somehow put into your graveyard without having been cast.

Memory's Journey — ruling 7

If the player is an illegal target by the time Memory's Journey resolves, the spell will have no effect, even if the cards are still legal targets. This is because a spell can't make an illegal target (the player) perform any actions (such as shuffling their library).

Memory's Journey — ruling 8

Any of the targeted cards that are illegal targets by the time Memory's Journey resolves aren't shuffled into their owner's library.

Memory's Journey : règles, fonctionnement et interactions (MTG)

Memory's Journey is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Target player shuffles up to three target cards from their graveyard into their library. Flashback (You may cast this card from your graveyard for its flashback cost. Then exile it.)

How it works : Memory's Journey

Original English text — Wizards of the Coast / Scryfall

#1March 19, 2021· Wizards of the Coast
If a card with flashback is put into your graveyard during your turn, you can cast it if it's legal to do so before any other player can take any actions.
No other card is named in this ruling.
#2March 19, 2021· Wizards of the Coast
"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."
No other card is named in this ruling.
#3March 19, 2021· Wizards of the Coast
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.
No other card is named in this ruling.
#4March 19, 2021· Wizards of the Coast
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.
No other card is named in this ruling.
#5March 19, 2021· Wizards of the Coast
A spell cast using flashback will always be exiled afterward, whether it resolves, is countered, or leaves the stack in some other way.
No other card is named in this ruling.
#6March 19, 2021· Wizards of the Coast
You can cast a spell using flashback even if it was somehow put into your graveyard without having been cast.
No other card is named in this ruling.
#7September 22, 2011· Wizards of the Coast
If the player is an illegal target by the time Memory's Journey resolves, the spell will have no effect, even if the cards are still legal targets. This is because a spell can't make an illegal target (the player) perform any actions (such as shuffling their library).
No other card is named in this ruling.
#8September 22, 2011· Wizards of the Coast
Any of the targeted cards that are illegal targets by the time Memory's Journey resolves aren't shuffled into their owner's library.
No other card is named in this ruling.
#9September 22, 2011· Wizards of the Coast
If no cards were targeted by Memory's Journey or if all the targeted cards are illegal targets by the time Memory's Journey resolves, the targeted player will still shuffle their library.
No other card is named in this ruling.
#10September 22, 2011· Wizards of the Coast
If you cast Memory's Journey with flashback, it won't be in the graveyard when you choose targets. It can't target itself.
No other card is named in this ruling.
#11September 22, 2011· Wizards of the Coast
You don't have to target any cards when you cast Memory's Journey, but you must target a player.
No other card is named in this ruling.