Can you cast a creature spell during another player's turn in a multiplayer game?

By default, creature spells follow sorcery-speed timing rules (CR 307.1), meaning you can only cast them during your own main phase when the stack is empty and you have priority. However, there are several important exceptions that allow casting creatures during another player's turn.

The most common exception is the keyword ability Flash (CR 702.8a), which allows a creature spell to be cast at any time you could cast an instant — including during other players' turns, in response to spells or abilities, during combat, etc. Many creatures have flash printed on them or can gain it through other effects.

Additionally, certain cards grant flash to all creatures you control (like Leyline of Anticipation or Vedalken Orrery), or allow you to cast spells as though they had flash. In these cases, any creature spell you own can be cast at instant speed during any player's turn.

You can also cast a creature spell during another player's turn if an effect specifically grants you the ability to do so — for example, some cards say 'you may cast creature spells as though they had flash' or grant permission via triggered abilities that go on the stack during another player's turn.

Example: It's your opponent's combat phase and they attack you. You control a Vedalken Orrery. You may cast Llanowar Elves (a creature with no flash) in response, as though it had flash, because the Orrery grants all your spells flash per its text and CR 702.8a.