Can I use Jax legend ability when defending a battlefield and a showdown starts?

Question

Accepted Answer

No, you cannot use the legend ability of **Grandmaster at Arms (Jax)** during a showdown.

**Ruling:**
Activated abilities that do not have the **Action** or **Reaction** keyword can only be activated during your turn when the game state is Open (the chain is empty). Because the legend ability of Grandmaster at Arms lacks these keywords, it cannot be used during a showdown, regardless of whether you are attacking or defending.

**Reasoning:**
*   **Ability Timing:** According to the rules for activated abilities, they must have a speed keyword (Action or Reaction) to be used during a showdown.
*   **Showdown State:** During a showdown, you are restricted to playing spells or activating abilities that are "legally timed" for that state (Rule 344). Since this ability does not have a speed keyword, it is not legally timed for use during a showdown.

This is my interpretation based on the standard rules for activated abilities and showdown timing. No official FAQ exists for this specific interaction.