If Hidden Blade is revealed from being face-down and the opponent responds by moving the targeted unit to a different battlefield, does the unit still die? Does the outcome differ if Hidden Blade is cast from hand instead?

Ruling: The outcome depends on whether Hidden Blade was played face-down or from hand. When revealed from face-down, if the unit is moved to a different battlefield it becomes an illegal target and does not die. When played from hand, the unit still dies because Hidden Blade only targets a battlefield (any battlefield), not a specific unit.

Nuances:

• Hidden Blade played face-down must target a unit at that specific battlefield, so moving the unit makes it an illegal target
• Hidden Blade played from hand only requires targeting a battlefield, not a specific unit, so moving the unit doesn't prevent it from dying