If you hide a card like Sprite Call that makes a unit at a battlefield, and all your units at that battlefield are killed before you play the hidden card, do you lose control of the battlefield immediately and what happens to the hidden card?

Ruling: When you lose control of a battlefield (by having no units there), any card hidden to that battlefield goes to the trash. You lose control immediately when your last unit dies, unless the battlefield is Contested (which only happens during showdowns).

Sequence:

• Your last unit at the battlefield dies
• You immediately lose control of the battlefield (unless it's Contested during a showdown)
• The hidden card goes to the trash

Nuances:

• During a showdown, you don't lose control of the battlefield until the showdown is done, even if all your units die
• A battlefield can only be Contested during showdowns
• This rule applies outside of combat/showdown timing as well