Can an opponent play a hidden Hidden Blade on my turn if their only unit (a temporary sprite) dies at the start of their turn, and I don't interact with that battlefield?

Ruling: If Hidden Blade is hidden, it can be played at reaction speed on your turn if you do something that can be reacted to, or as a reaction to the Temporary trigger at the start of the opponent's turn (killing the sprite to draw 2 cards before it dies to Temporary). If you have no triggers and don't give a reaction window during your turn, the opponent cannot play it on your turn.

Sequence:

• At start of opponent's turn, Temporary trigger occurs
• Opponent can react to this trigger by playing hidden Hidden Blade to kill their sprite and draw 2 cards before it dies to Temporary
• If opponent doesn't use this window, and you don't provide reaction windows on your turn, Hidden Blade cannot be played

Nuances:

• If Hidden Blade is not hidden (played from hand), it's Action speed and can only be played during showdowns
• You can begin and end your turn without giving reaction windows if you have no triggers and don't take actions that allow reactions