If I have a location with temporary AND a hidden card, can I react before the location leaves the battlefield at the start of the beginning phase?

Ruling: Yes, you can react to the temporary trigger before the location leaves the battlefield.

Sequence:

• Temporary triggers at the start of the beginning phase
• The triggered ability is put on the chain
• Priority is granted when triggered abilities are put on the chain
• You can play reactions (including hidden cards) when you have priority
• After the chain resolves, the location leaves the battlefield

Nuances:

• Temporary is a triggered ability keyword, so it follows the normal rules for triggered abilities and priority