If I have a buffed unit that is in my base and being affected by my opponent's The List and it is targeted twice by their Falling Star, if the first damage instance of Falling Star would kill the unit what would happen if I use my Sett the Boss to save it?

Regarding Sett, The Boss and the interaction with Falling Star:

The Interaction

1. Falling Star Resolution: When Falling Star resolves, it executes its instructions top-to-bottom: "Deal 3 to a unit. Deal 3 to a unit."
2. First Instance of Damage: The first 3 damage is dealt to your buffed unit in your base. If this damage is lethal, Sett, The Boss’s ability intercedes as a replacement effect.
3. Sett’s Replacement Effect: Instead of the unit being destroyed, the effect replaces the "destroy" event with a "recall" event.
   • Recall: Per Rule 450 and the 2025-10-24 Patch Notes, a Recall is the relocation of a permanent to its controller's Base. It is not a move, and it does not move the card to your hand.
   • Buff Spent: Per the FAQ and Sett's card text, you must spend the unit's buff as the cost for this replacement effect. The unit is recalled to your base in an exhausted state.
4. Second Instance of Damage: Because the unit remains in your base after being recalled, it is still at the same location. Therefore, it remains a legal target for the second instance of damage from Falling Star.

Summary

• Sett's Save: Your unit is not destroyed. It is recalled to your base (not your hand), is exhausted, and its buff is removed.
• Second Damage: The second instance of damage from Falling Star will still hit your unit, as it is still at your base and remains a legal target.
• The List: As your unit remains at your base following the recall, it is still a valid target for The List if the unit still has the named tag.

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