My opponent used salvage to target a gear equipped on a unit I control at a battlefield. In reaction, I sacrifice this unit. Does the salvage trigger since the gear is now on base?

To determine if Salvage still triggers, we must look at how targeting and resolution work in Riftbound.

Ruling

Yes, Salvage will still resolve.

According to Rule 355.10, targeting choices are locked when the card is played (added to the chain). When your opponent played Salvage, they targeted the gear while it was attached to your unit at the battlefield. Because the target was legal at the time of play, the spell remains on the chain targeting that specific gear.

What happens to the gear?

When you sacrificed your unit, the attached gear became un-attached. Under Rule 452.1 and Rule 149.3, un-attached gear at a battlefield are recalled to their controller's base during the next cleanup.

Even though the gear moves to the base, the Salvage spell is still tracking that specific object as its target. When Salvage resolves:

1. It attempts to execute its instruction: "Kill up to one gear." Since the targeted gear is now at your base, it is still a valid target for the kill effect.
2. Even if the gear could not be killed (though it can be), Salvage would still proceed to its next instruction: "Draw 1."

Sequence of Events

1. Opponent plays Salvage: They target your attached gear at the battlefield. Salvage is now on the chain.
2. You react: You sacrifice your unit. The gear detaches.
3. Chain resolves (LIFO):
   • The Salvage effect checks for its target. It is still the same gear (now located at your base).
   • The effect "kills" the gear (it is sent to the trash).
   • The effect "Draw 1" resolves.

Note: This is my interpretation based on standard targeting and resolution rules (355.10) and the mechanics of Gear movement (452.1). No official FAQ exists for this exact interaction, but it follows the established behavior that spells "stick" to their targets even if those targets change location, provided the target remains valid.