How long do I have to legally remember that Darius needs to be ready after my second card cast?

Question

Accepted Answer

To determine how long you have to acknowledge the triggered ability of **Darius, Trifarian**, we must look at the tournament rules regarding triggered abilities and "observable impact."

According to **Tournament Rules 2026-03-30, Rule 506.3**, the accountable player (you, as the controller of Darius) must acknowledge their triggered abilities by the time they would have an "observable impact" on the game. If you do not acknowledge the trigger before a new game action is taken after that point of impact, the trigger is considered forgotten.

### When is the point of observable impact?
For **Darius, Trifarian**, his ability triggers when you play your second card of the turn. The ability has an observable impact because it modifies his Might and readies him.

According to **Tournament Rules 2026-03-30, Rule 506.3.d.4** and **506.3.d.6**:
*   A trigger that gives a unit +Might does not have an immediate observable impact until that Might becomes relevant (e.g., during combat).
*   A trigger that causes a unit to ready **does** have an observable impact.

Therefore, you must acknowledge the trigger and place it on the chain before you take any subsequent game action (such as playing a third card, initiating combat, or passing priority to your opponent) that would be affected by Darius being ready or having +2 Might.

### Summary of the Requirement
*   **Deadline:** You must acknowledge the trigger before taking any new game action after the second card has resolved.
*   **Consequence:** If you take a new game action (e.g., playing a third card or passing priority) without acknowledging the trigger, the ability is considered forgotten and will not be placed on the chain (**Rule 506.4**).
*   **Note:** Because Darius is a "When you play" trigger, he enters the board first, and his ability triggers immediately after he resolves as the second card of the turn. You have the opportunity to place this on the chain as part of the resolution process of that second card.

This is my interpretation based on the Tournament Rules regarding triggered abilities and observable impact. No official FAQ exists specifically for the "time limit" of this trigger beyond the general rules for missed triggers.