Can an opponent react to Forge of the Future by casting a reaction that kills a unit to bring back Immortal Phoenix from trash before the recycle resolves, and would they then get to target a new card in trash?

Ruling: Yes, opponents can react to Forge of the Future's activation before it resolves. If they kill a unit with a reaction spell, Phoenix's trigger is added to the chain immediately and will resolve before Forge can, allowing Phoenix to be played from trash. However, the cards targeted for recycling are chosen on activation and cannot be changed - if Phoenix was declared as a recycle target and gets played, you lose that recycle.

Sequence:

• Forge of the Future activates and targets cards in trash for recycling
• Opponent can react to the activation before it resolves
• If opponent kills a unit with a reaction spell, Phoenix's trigger is added to the chain immediately
• Phoenix's trigger resolves before Forge resolves
• Phoenix is played from trash
• Forge resolves, but if Phoenix was targeted for recycle, that recycle is lost

Nuances:

• Phoenix doesn't specify enemy unit, so you can kill your own units to trigger it
• You could hypothetically react to Forge with a spell on your own unit to trigger Phoenix