If I target a unit at a battlefield with Void Seeker and the unit moves to a different battlefield, does Void Seeker still hit?

Ruling: Void Seeker will still hit the unit as long as it remains a legal target. A unit that moves from one battlefield to another is still "at a battlefield" even though it is no longer "here" at the original battlefield.

Nuances:

• Hidden Blade works differently - if the targeted unit moves from the battlefield where Hidden Blade is hidden, Hidden Blade will not kill the unit and you do not draw a card
• The distinction is between "at a battlefield" (any battlefield) vs "here" (the specific battlefield)