Flash
Keyword abilities
Cast this spell any time you could cast an instant.
How it works
Flash lets you cast a spell at instant speed — on any player's turn, whenever you have priority, including in response to other spells and abilities.
It changes only when you may cast the spell. It doesn't change the cost, and it isn't haste.
Common confusions
“I flashed in a creature on an opponent's turn — can it attack or tap right away?”
Flash isn't haste. The creature still has summoning sickness until you've controlled it continuously since your most recent turn began.
“Flashing a blocker in during combat.”
Legal and a classic trick — cast it before blocks (e.g., end of the declare-attackers step) and it can block this combat since it isn't attacking.