If I move my unit targeted with Hidden Blade to another battlefield with Tideturner, does it still target my unit?

Whether your unit is successfully saved from Hidden Blade depends on how that Hidden Blade was played.

According to Core Rule 811.1.d.2, when a spell or permanent is played from "Hidden," any targets chosen must be selected from among options at the battlefield where it was hidden. This creates a specific targeting restriction for hidden cards. Tideturner acts as an exception to standard targeting due to the explicit targeting restriction in its own text, which allows it to function as intended (as clarified in FAQ #7907 and FAQ #6517).

The Interaction Outcome

• If Hidden Blade was played from your opponent's hand: According to the logic in FAQ #7179, a standard Hidden Blade played from the hand only requires the target to be a unit at any battlefield. Because the targeting relationship is established with the unit itself, moving that unit to a different battlefield does not break the targeting. Hidden Blade will still kill your unit at its new location.

• If Hidden Blade was played from "Hidden": Per Core Rule 811.1.d.2 and FAQ #210/FAQ #2461, when Hidden Blade is played from "Hidden," it is restricted to targeting a unit at the specific battlefield where it was hidden. If you use Tideturner (played from hidden at another location) to move your unit to a different battlefield in response, the target for Hidden Blade becomes illegal (it no longer meets the targeting restriction of being at the original battlefield). When Hidden Blade resolves, it will "mistarget" and have no effect; your unit will survive, and no cards will be drawn. In this scenario, you successfully dodge the effect.

Summary of Rules

• Targeting Restriction: Rule 811.1.d.2 dictates that hidden spells must target units at the battlefield where they were hidden.
• Mistargeting: Rule 359.3.e.9 defines that if a target becomes invalid (e.g., it moves to a location that no longer satisfies the spell's restriction), the spell mistargets.
• Official Rulings: As noted in FAQ #210, while this works for Hidden Blade, it is a specific interaction based on the "Hidden" targeting restriction; other cards (like Riptide Rex) that do not have this restriction behave differently.