If my opponent plays Hidden Blade and I move a unit to another battlefield, does my unit survive?

Whether your unit survives a Hidden Blade targeting depends on whether the card was played from your opponent's hand or from a Hidden (facedown) state.

1. If Hidden Blade was played from the HAND

Your unit does NOT survive. Per RiftJudge FAQ #7179, when Hidden Blade is played from the hand, the targeting requirement is simply that the unit must be at a battlefield. It does not lock the target to a specific battlefield location.

• Sequence: Your opponent plays Hidden Blade targeting your unit at Battlefield A. In response, you move your unit to Battlefield B.
• Result: Because the unit is still at a battlefield, it remains a legal target. The spell resolves and kills the unit at its new location.

2. If Hidden Blade was played from HIDDEN

Your unit SURVIVES. Per RiftJudge FAQ #2461, cards played from a Hidden state carry an implicit targeting restriction that the target must be at the battlefield where the card was hidden (the "here" requirement).

• Sequence: Your opponent plays Hidden Blade from a facedown zone at Battlefield A, targeting your unit at Battlefield A. In response, you move your unit to Battlefield B.
• Result: Because the target is no longer at the battlefield where the Hidden Blade originated, the spell mistargets. The instruction is ignored, and your unit survives.

Summary Table

Note: Per FAQ #35, if you move your unit to your Base, the unit survives regardless of whether the spell was played from hand or hidden, as it no longer meets the targeting requirement of being at a battlefield.

Note: I could not fully verify the classification of the Base as a non-board zone against the retrieved rules.