Does the reflection token stay as a 0 might unit or does it completely fizzle when LeBlanc makes a reflection of a unit and I react to this by gusting said unit?

In this scenario, the Reflection token does not "fizzle." Instead, it will enter the battlefield as a 0 [M] unit, but it will fail to become a copy of the targeted unit.

Here is the breakdown of why this happens based on the timing of the chain:

1. Chain Sequence

• Chain Item 1: The Deceiver ability (triggered).
• Chain Item 2: Gust (played in reaction).

Because the chain resolves in Last-In, First-Out (LIFO) order, Gust resolves first.

2. Resolution Order

1. Gust Resolves: You return the target unit to its owner's hand. That unit is no longer at the battlefield.
2. Deceiver Ability Resumes: The ability continues to execute its instructions in order:
   • "Play a ready Reflection unit token there": This instruction succeeds. A 0 [M] Reflection token enters the battlefield.
   • "Then do this: It becomes a copy of another unit there": This instruction attempts to resolve. However, the original target unit is no longer at that battlefield.
   • Result: Because the target is no longer available to be copied, the copy effect cannot be applied. The "do all you can" rule applies here: the ability continues as much as possible, but since it cannot find a valid target to copy, the Reflection token remains at its base state: a 0 [M] unit without the rules text or stats of the intended target.

Important Note on "Fizzling"

In Riftbound, spells and abilities do not "fizzle" (vanish without doing anything). If part of an instruction becomes impossible to fulfill (such as targeting a unit that is no longer there), that specific instruction is skipped, and the game proceeds with the next instruction or concludes the effect.

Summary: The Reflection token successfully enters play, but since its "copy" target was removed by Gust before the copy instruction could execute, it remains a base 0 [M] Reflection token.