If a unit is targeted by a spell that requires the unit to be at a battlefield (like Voidseeker or Hextech Ray), and the opponent uses Flash to move that unit back to base in response, does the spell's damage fizzle?

Ruling: When a unit is moved from the battlefield to base in response to being targeted by a spell that targets units at a battlefield, the unit becomes an invalid target and the spell's damage will not be dealt.

Nuances:

• Voidseeker will still give you a draw even though the damage doesn't resolve, because of the "do all you can" rule