If a temporary unit dies and there's a hidden card on that battlefield, can you reveal the hidden before cleanup removes it?

Ruling: Yes, you can reveal and play the hidden card before losing it. When the temporary unit's triggered ability resolves at the start of your turn, it starts a chain which gives you a window to play the hidden card before the unit dies and you would lose control of the battleground.

Sequence:

• At the start of your turn, the temporary unit's triggered ability goes on the chain
• This creates a window where you can play the hidden card
• After the chain resolves, the temporary unit dies
• If you no longer control the battleground after the unit dies, the hidden would be trashed

Nuances:

• A cleanup occurs when an item on the chain resolves, not just at end of turn
• If you play another temporary unit during this window, it won't die until your next turn