Can you activate a hidden Consult the Past on your opponent's turn even if they aren't attacking the battlefield with the hidden card, and can you activate it at reaction speed without the opponent starting a chain?

Ruling: You can activate hidden Consult the Past on your opponent's turn at reaction speed, but you must be in a showdown or reacting to a spell or ability. The hidden card does not need to be at the same battlefield being attacked.

Sequence:

• You can activate the hidden card whenever you have priority
• This includes when you have focus and priority during a showdown
• Or in response to your opponent's spells/triggers

Nuances:

• You cannot activate it the same turn it was hidden
• During the combat damage step, no one gets focus or priority, so you cannot reveal the hidden card at that point
• You must reveal during the showdown when you have priority, not after damage calculation