Passing and resolving

The combat showdown defined Priority as the exclusive right to take appropriately timed actions, and left how it moves while a chain exists for later. This is later. At any given time, up to one player has Priority.¹Rule 312. At any given time, up to one player has Priority. Open in the rules browser

Tasks, then FEPR

A task is one or more steps or processes that players must perform before continuing with any other actions.²Rule 333. A Task is one or more steps or processes that one or more Players must perform before continuing with any other actions. Open in the rules browser Cleanups are tasks, and so are the actions of the Start of Turn, the steps of combat and the actions at the end of the turn.³Rule 333.1. Tasks include, but are not limited to: Cleanups, the actions performed during the Start of Turn Process, throughout Combat in its various steps, and the actions performed during the End of Turn Process. See rule 318. Cleanups for more information on Cleanups See rule 315. Start of Turn for more information on the Start of Turn process See rule 459. Combat for more information on the steps of Combat See rule 317. Ending Phase for more information. Open in the rules browser Whenever a player takes actions that incur tasks, the rules give the order to work through as HOT FEPR: Handle Outstanding Tasks, then Finalize, Execute, Pass, Resolve.⁴Rule 334. Whenever a Player takes one or more actions that incur Tasks they should refer to the process of HOT FEPR: Handle Outstanding Tasks; then Finalize, Execute, Pass, Resolve. Open in the rules browser

FEPR is the loop a chain runs through. Its four steps are these.

1. Finalize. The controller of the oldest Pending item completes the steps of playing it until it is Finalized or leaves the chain.⁵Rule 337.1. If there is at least one Chain Item Pending, the controller of the oldest Pending Chain Item must complete the steps of Playing that Pending Item until it is a Finalized Item or leaves the Chain. See rule 349. Playing Cards for more information on finalizing chain items. Open in the rules browser Items are finalized in the order they were added to the chain⁶Rule 337.1.b. Chain Items are Finalized in the order they were appended to the Chain. Open in the rules browser, and finalizing an item does not pass Priority.⁷Rule 337.1.a. Finalizing an item to the chain does not pass Priority. Open in the rules browser When nothing is left to finalize, the controller of the next item on the chain gains Priority.⁸Rule 337.4. If, after finalizing the Chain Item, there are no more items on the chain to be Finalized, the controller of the next item on the chain gains Priority. Move to step 2: Execute. Open in the rules browser That is the path of an item that lingers, such as a spell; The chain showed that a permanent and an ability that adds resources do not wait there.
2. Execute. The player with Priority may play a card or activated ability that is legally timed⁹Rule 338.1.a. Play a Card or Activated Ability that is legally timed. Open in the rules browser. On a chain that means one with Reaction, as The combat showdown said, or one that will have Reaction when played.¹⁰Rule 338.1.a.2. A Legally Timed Card or Activated Ability would be one with Reaction or one that will have Reaction when played under appropriate circumstances. Open in the rules browser Playing one creates a new Pending item, and play returns to Finalize.¹¹Rule 338.1.a.7. Playing a Card or Activated Ability will create one or more Pending Items. Return to Step 1: Finalize. Open in the rules browser Instead of playing, the player with Priority may pass it to the next player in turn order.¹²Rule 338.1.b.1. The player with Priority passes Priority to the next Player in Turn Order. Proceed to Step 3: Pass. Open in the rules browser
3. Pass. If all players have passed Priority in sequence without adding anything to the chain, play goes on to Resolve.¹³Rule 339.1. If all players have passed Priority in sequence without adding any items to the Chain, proceed to Step 4: Resolve. Open in the rules browser Otherwise, play returns to Execute.¹⁴Rule 339.2. Otherwise, the player with Priority passes Priority to the next Player in Turn Order. Return to Step 2: Execute. Open in the rules browser
4. Resolve. The newest Finalized item resolves.¹⁵Rule 340.1. The newest Finalized Chain Item resolves. Execute its game effects in their entirety. See rule 349. Playing Cards for more information on resolving spells. See rule 398. Playing or Activating Abilities for more information on resolving abilities. Open in the rules browser Then, if Pending items remain, play returns to Finalize.¹⁶Rule 340.3. If the Chain is not empty and there are one or more Pending Items, return to Step 1: Finalize. Open in the rules browser If items remain and none of them is Pending, the controller of the newest item gains Priority and play returns to Execute.¹⁷Rule 340.4. If the Chain is not empty and there are no Pending Items, the controller of the newest item on the chain gains Priority. Return to Step 2: Execute. Open in the rules browser If the chain is empty, play proceeds in an Open State.¹⁸Rule 340.2. If the Chain is empty, play proceeds in an Open State. Open in the rules browser

Three things the loop means

Starting a chain with a spell does not hand Priority to your opponent. When your spell starts a chain, it is the only item on it, so once it is finalized Priority comes back to you, and you may even add another item before anyone else acts.¹⁹Rule 338.1.a.5. This can be an additional item to the item that Started the Chain in the case of the first player with Priority after creating the Chain. Open in the rules browser Your opponent can answer only once you pass Priority to them.

Only one item resolves at a time. If items remain and none is Pending, play goes back to Execute, so players get another chance to act before the next item resolves.

Newest first means the last thing added is the first to happen. A spell with Reaction played onto a chain resolves before the spells and abilities that were already on it.²⁰Rule 159.2.b.3. This will result in this spell resolving before spells and abilities that are already on the chain. See rule 813. Reaction for more information. Open in the rules browser A spell's game effects are executed, and then its card is placed in the trash.²¹Rule 351.2. Spells create game effects that are executed, then the card is placed in the trash when Played. Open in the rules browser

The walkthrough in the next lesson steps through a chain like this one, frame by frame.