Can you react with Gust to the "move a friendly unit" portion of Relentless Pursuit before the equipment is attached to the unit?

No, you cannot react to the "move a friendly unit" portion of Relentless Pursuit to prevent or interrupt the attachment of an equipment.

Here is the breakdown of why this interaction functions this way:

1. The Chain and Resolution

When you play Relentless Pursuit, you place it on the chain. Because it is a spell, this creates a Closed State. Once the spell is on the chain, players have the opportunity to play reactions (like Gust) before the spell resolves.

2. Resolution is Atomic

When Relentless Pursuit resolves, its instructions are performed in the order they are written on the card:

1. Move the friendly unit.
2. Attach an equipment (optional).

Crucially, a spell resolves as a single, uninterrupted event. Once Relentless Pursuit begins resolving, it does not stop or allow for new reactions between its instructions (moving the unit and attaching the equipment).

3. Why You Cannot "Intervene"

If you play Gust in response to Relentless Pursuit (before the spell resolves), Gust will resolve first due to LIFO (Last-In, First-Out) timing.

• If Gust successfully returns the target unit to its owner's hand, the unit is no longer on the battlefield.
• Because the unit is no longer a valid target or no longer on the board, the subsequent instructions of Relentless Pursuit (moving it and attaching equipment to it) will fail to resolve on that unit.

However, you cannot let the move happen and then "interrupt" the spell after the move but before the attachment. By the time you have the opportunity to play a reaction, you must do so before the spell's resolution begins. Once the spell begins to resolve, it completes all of its instructions without pause.