When a hidden card is played and its target is moved to a different battlefield before resolution, does the spell mistarget due to hidden targeting rules?

Ruling: Yes, the spell will mistarget (whiff). When a card is played from hidden, it adds "here" to the targeting requirement, and this restriction is maintained when checking valid targets on resolution.

Sequence:

• Hidden Blade is played from hidden at battlefield B, choosing the Poro at battlefield B
• In response, Tideturner swaps the Poro to battlefield A
• When Hidden Blade resolves, it checks if the target meets its targeting requirements
• The Poro is no longer at the battlefield where Hidden Blade was hidden ("here")
• Hidden Blade mistargets because the target no longer meets the targeting requirements established by the hidden rules

Nuances:

• The target was valid when chosen during finalization, but targeting requirements are checked again on resolution
• Playing from hidden modifies the spell's targeting requirements to include "here" (the battlefield where it was hidden), and this modification persists through resolution