Quick rules question about LeBlanc, Deceiver and Ambush: After I put her initial trigger on the chain (paying the discard cost), can I respond to it by playing an Ambush unit like Chakram Dancer? And if that Ambush unit resolves first, can I then choose that newly played Chakram Dancer as the target for the Reflection token's reflexive copy trigger?

Yes, you can absolutely do this. Because LeBlanc, Deceiver's "When you conquer or hold" ability is a triggered ability that uses the chain, it creates a Closed State when placed on the chain. This allows you to play your Chakram Dancer as a [Reaction] using its Ambush keyword.

The Sequence

1. Triggering: You conquer or hold a battlefield. LeBlanc's ability triggers. You place it on the chain and pay the required costs (discarding a card and exhausting LeBlanc).
2. Adding the Ambush Unit: While LeBlanc’s trigger is on the chain (a Closed State), you play Chakram Dancer to that battlefield. Because it has Ambush, you are permitted to play it at [Reaction] timing.
3. Resolving the Unit: The unit enters the chain as a pending item and, per RiftJudge FAQ #9978, immediately finalizes and enters the battlefield.
4. Priority/Reaction Window: Once the unit has entered play, priority is returned to you. You can choose to pass priority.
5. Chain Resolution: The chain resolves in Last-In, First-Out (LIFO) order.
   • LeBlanc’s ability resolves: You create the 0 [M] Reflection token on the battlefield.
   • Because the ability includes a reflexive trigger ("Then do this: It becomes a copy of another unit there..."), this trigger is added to the chain as a new, separate pending item.
6. Reflexive Target Selection: You choose the target for the copy effect when the reflexive trigger is placed on the chain (the finalization step). Since your Chakram Dancer is already on the battlefield, it is a valid choice.

Summary

• Targeting Timing: As clarified in the Zilean, Time Mage ruling (2026-04-29), the unit chosen to be copied by Deceiver's reflexive trigger is chosen upon the finalization of that reflexive trigger.
• Legality: Because the target selection happens after the unit has already resolved and entered the battlefield, Chakram Dancer is a perfectly legal target for the reflection token to copy.

Note: I could not fully verify this ruling against the retrieved rules.