How many times can I react during the effect of Leblanc deceiver? What are the different windows where I can play a gust?

To answer your question, we first need to clarify the timing of LeBlanc, Deceiver's ability and how Gust interacts with it.

1. How many times can you react?

There is no fixed limit to how many times you can react to the chain created by LeBlanc’s ability.

Because LeBlanc's ability is a triggered ability ("When you conquer or hold..."), it uses the chain. Once the trigger is placed on the chain, a Closed State begins. During this time, players can take turns adding [Reaction] cards to the chain (including Gust) until both players pass consecutively.

2. What are the windows where you can play Gust?

You can play Gust (which has the [Reaction] keyword) whenever there is an item on the chain, or when the state is open. Specifically, regarding the resolution of LeBlanc's ability:

1. Reacting to the Ability Trigger: When you trigger the ability, it is placed on the chain. Players have a window here to play Gust before the ability resolves. If you play Gust here, it will resolve first (LIFO — Last In, First Out).
2. Reacting to the Reflection Token: As LeBlanc’s ability resolves, it creates a Reflection unit token. According to Riftbound rules, units enter the chain immediately and then finalize. While you cannot react to the unit entering the board, you can react to any triggered abilities that occur as a result of that unit entering play (if any existed).
3. Reacting to the Reflexive Trigger: The latter part of LeBlanc's ability ("It becomes a copy of another unit there...") is a reflexive trigger. This means it is a separate effect that goes onto the chain after the initial ability resolves. This provides a new window to play Gust before the token becomes a copy of another unit.

Sequence Summary

• Trigger: LeBlanc's ability is added to the chain.
• Window 1: Players can play Gust (or other reactions).
• Resolution: If no Gust prevents the ability, the ability resolves:
  • The Reflection token is created.
  • The reflexive trigger ("It becomes a copy...") is placed on the chain.
• Window 2: Players can play Gust in response to the reflexive trigger before the token becomes a copy.

Note: This is my interpretation based on the standard rules for triggered abilities and the reflexive targeting mechanic described in the Core Rules (Rule 359). No official FAQ specifically lists the number of reaction windows for LeBlanc, but this follows the established Riftbound chain and priority timing.