Can Reaction spells/units be used mid-chain (similar to Magic's stack), allowing multiple Reactions to be played before earlier spells resolve?

Ruling: Yes, Reactions can be used mid-chain. The chain resolves one link at a time, and new Reactions can be added after it's started resolving, with the last Reaction played resolving first.

Sequence:

• Player A plays a spell (e.g., Cleave)
• Player B responds with a Reaction
• Player A can respond with another Reaction before the first Reaction resolves
• The chain resolves last-in-first-out (most recent Reaction resolves first)

Nuances:

• Spells in the chain can fizzle if their requirements are no longer met (such as losing a valid target)
• Example: If Cleave targets a unit, but an opponent uses Gust to return that unit to hand before Cleave resolves, Cleave fizzles due to having no valid target