When can you use LeBlanc's Legend ability?

You can use LeBlanc, Deceiver's ability when the trigger condition is met: "When you conquer or hold."

Because this is a triggered ability, it functions differently than activated abilities. Here is the breakdown of how and when it can be used:

Timing and Execution

1. Trigger Condition: The ability triggers specifically when you conquer a battlefield or hold a battlefield.
2. Optionality: Because the ability text uses "you may," the trigger is optional. When you conquer or hold, you decide whether or not to place the ability on the chain.
3. Cost: As a cost to place the ability on the chain, you must discard 1 card from your hand and exhaust LeBlanc. According to RiftJudge FAQ #10237 and #10107, you cannot activate this ability if you have no cards in hand to discard, as the cost must be paid in full to place the ability on the chain.
4. Chain & Interaction: Once placed on the chain, it creates a Closed State. This allows you and your opponent to play [Reaction] cards to interact with the ability or the resulting effects (as detailed in RiftJudge FAQ #10329).

Important Considerations

• Targeting: The Reflection token's ability to become a copy of another unit is a reflexive trigger. This means you choose the target unit for the copy effect when that specific part of the ability resolves, not when you first trigger LeBlanc (see RiftJudge FAQ #10329).
• Existing Units: If there are no other units at the battlefield when the reflection token enters play, there is no valid target for the copy effect.
• Triggering Events: The ability is strictly tied to the "conquer" or "hold" event. It cannot be activated manually at other times.

This is my interpretation based on the card text and official FAQs. No further official rules text is needed to clarify this trigger timing.