If someone piercing lights my Draven while he is at a battlefield, but I react with Fight or Flight and move Draven back to base, does Draven still get hit with Piercing Light if there are no longer any units at that battlefield?
No, Draven will not be hit by Piercing Light in this scenario.
According to the rules and established FAQs for Piercing Light:
- Targeting Requirements: Piercing Light specifies that it deals damage to "a unit at a battlefield."
- Invalid Targets: When a unit is moved from the battlefield to the base in response to being targeted by a spell that requires the unit to be at a battlefield, the unit becomes an invalid target. Consequently, the spell's damage will not be dealt to that unit.
Because you used Fight or Flight to move Draven to your base in response to Piercing Light, Draven is no longer at a battlefield when the spell attempts to resolve. Therefore, he is no longer a legal target for the damage, and the effect fails to deal damage to him.