What happens when I play Long Sword with Quickdraw and my opponent reacts with a Gust?

To resolve this interaction, we look at the chain timing and the targeting requirements of Gust.

The Sequence of Events

1. Playing the Gear: You play Long Sword from your hand. You pay its cost. It enters the battlefield at your base immediately. As established in RiftJudge FAQ #9577, playing a Gear card itself does not use the chain and cannot be reacted to.
2. Triggered Ability: The Quick-Draw keyword triggers: "When you play this, attach it to a Unit you control." This ability is placed on the chain and targets a unit you control.
3. Reaction Window: Because this triggered ability is now on the chain, your opponent gains priority and plays Gust as a reaction.
4. Opponent's Target: Your opponent targets your unit with Gust. For Gust to be a legal play, your unit must have 3 Might or less (as stated on the Gust card text).
5. Resolution (LIFO): The chain resolves in Last-In, First-Out order:
   • Gust Resolves: Gust checks if its target is still on the battlefield and still meets its targeting requirement (3 Might or less). If it does, Gust returns your unit to your hand.
   • Attachment Fails: The Quick-Draw triggered ability then attempts to resolve. Because your unit is no longer on the battlefield, the target is now illegal/invalid. As established in RiftJudge FAQ #9577, the ability "whiffs" (resolves with no effect), and the Long Sword remains at your base unattached.

Important Clarifications

• Targeting: Gust requires the target to have 3 Might or less. If your unit has 4 or more Might, Gust is not a legal response to your Quick-Draw trigger.
• Failure to Attach: The Long Sword is not destroyed or sent to the trash when the attachment fails; it remains at your base. You may use its Equip ability later to attach it to a unit.
• Legality: According to RiftJudge FAQ #36, if a unit's Might were increased to 4 or higher in response to Gust (e.g., by a separate reaction), the Gust would effectively fizzle because the unit would no longer meet the targeting requirement upon resolution.

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