Changes

There are two types of actions a player may can make: actions that start a chain Chain (actions with a spell speedSpell Speed), and actions that do not start a chain Chain (actions without a spell speedSpell Speed). Whether or not an action starts a chain Chain determines how players are able to respond to the action in accordance with fast effect timing. Remember: if something activates, then it starts a chainChain. If something does not activate, it does not use the chainChain.

If your action has a spell speed, then it starts a chainChain. Activating a Spell or /Trap Card or Effect, or effect and activating the effect of a monster, all have spell speeds Spell Speeds and all start chainsChains.

If the action does not have a spell speedSpell Speed, then it does not start a chain Chain (it does not activate). Performing a Normal/Synchro/Xyz Summon, setting Setting a card, declaring an attack, drawing for your normal draw, etc.

All actions can be responded to by either player with fast effects in accordance with the "[[Fast Effect Timingeffect timing]] Chart" chart.

If an effect activates “when” an action that has a Spell Speed occurs, you must activate that effect in the very next chain linkChain Link. If there is a chain link Chain Link between the activation and the effect you want to respond with, it is no longer “when” that action has occurred, and you can no longer respond to that activation.

* Player A [[Tribute Summon]]s "[[Caius the Shadow Monarch]]" by tributing "[[Sangan]]". Player A activates the effect of "[[Sangan]]" as Chain Link 1, and the effect of "[[Caius the Shadow Monarch]]" as Chain Link 2. If Player B activates "[[Solemn JudgmentStrike]]" as Chain Link 3, it can only be in response to "[[Caius the Shadow Monarch]]’s" effect, as this is the effect it is being chained directly to. It is not “when” "[[Sangan]]"’s effect is activated.

There are many actions which a player can perform that do not have a spell speed, and thus do not use the chainChain. These are all actions which players can respond to. It is important to note that although the actions may all be different, the mechanics governing how you respond to them are all the same.

With respect to actions that do not have a spell speedSpell Speed, so long as that action was the last thing to occur, it is still “when” that action occurs for as long as that action was the last thing to happen (cards being activated in a chain Chain do not count). Or, alternatively, all cards and effects in the very next chain Chain are being activated in response to the event which is the last thing to happen.

* Player A declares an attack with "[[Blue-Eyes White Dragon]]". Player B activates "[[Magic Cylinder]]" as Chain Link 1. Player A activates "[[Book of Moon]]" as Chain Link 2. This chain Chain then resolves. In Box C, Player B is not able to activate "[[Mirror Force]]", as the last thing to happen was not an attack being declared.  * Player A controls a face-up "[[Magical Meltdown]]" and activates "[[Polymerization]]", fusion summoning "[[Elder Entity Norden]]", whose effect activates as Chain Link 1. The opponent, Player B, cannot activate any cards or effects in response to the effect of "[[Elder Entity Norden]]". Even if Player A adds a new effect as Chain Link 2, Player B still cannot activate a card or effect, as it is still "when" "[[Elder Entity Norden]]" is Fusion Summoned by the effect of "[[Polymerization]]". This also does not change if Player A chooses not to activate the effect of "[[Elder Entity Norden]]".