When you have hidden cards at a battlefield with Ravenbloom Student and your unit is removed, do you have to reveal all hidden cards or can you choose to reveal only some to maintain battlefield control?

Ruling: You can choose to reveal only one hidden card in response to removal effects to maintain battlefield control. You are never required to reveal all hidden cards at once.

Sequence:

• When an opponent plays a card that would remove your unit, you can respond by playing a hidden unit to the battlefield
• You only need to play one hidden unit to maintain control, not all of them
• During combat, if you choose not to play hidden cards and lose control of the battlefield, all hidden cards go to the trash
• Outside of combat, if your units are removed you immediately lose control in the cleanup that follows, and hidden cards go to trash unless you respond

Nuances:

• During combat, you maintain control of the battlefield until the end of combat even if your units are removed, giving you a window to play hidden units
• When multiple triggers target your unit (like Icathian Rain), all targets are locked in when triggers go on the chain - they cannot retarget to newly revealed hidden units
• You can wait until you have focus during combat to play hidden units if that's more advantageous