When Falling Star targets two units (one at base, one at battlefield) and Zhonya's Hourglass is hidden, can the player choose which unit to save by revealing Zhonya's between the two damage instances?

Ruling: Yes, if Zhonya's Hourglass is still hidden after Falling Star's two targets have been declared, you can reveal and play it between the damage instances to save whichever unit you choose. The key is waiting for the targets to be announced before revealing Zhonya's.

Sequence:

• Falling Star is played and resolves, creating two reflexive triggers that announce targets and order
• If Zhonya's remains hidden at this point, wait for the first target to be dealt damage
• If the first target is the unit you don't want to save, let it die
• Reveal and play Zhonya's before the second damage instance to save the unit you want to protect

Nuances:

• If you reveal and play Zhonya's before Falling Star's targets are declared, your opponent can order the targets to force you to use it on a specific unit
• Hidden cards have no effect while hidden - Zhonya's only works when fully played (in your base)
• A unit saved by Zhonya's heals to full health, exhausts, and recalls while keeping any buffs (since it doesn't change zones)