If my opponent plays Brynhir Thundersong off of my Promising Future, what happens to the card I chose to play? Can I still play it even though Brynhir's effect prevents playing cards?

Ruling: When Brynhir Thundersong is played from Promising Future, your chosen card can still resolve normally. Brynhir's "When You Play Me" (WYPM) effect that prevents opponents from playing cards only applies after all cards from Promising Future have already been played and placed on the chain as pending items.

Sequence:

• Promising Future begins resolving, all players banish one card from top 5
• Starting with next player in turn order, players play their banished cards (these go on chain as pending)
• Brynhir is played and goes pending, then your card is played and goes pending
• Pending items finalize in the order they were put on the chain
• Brynhir finalizes first and immediately resolves, her WYPM effect goes on the chain pending
• Your card finalizes next (now on the chain above Brynhir's WYPM)
• Brynhir's WYPM resolves, preventing further card plays
• Your card (already played and on the chain) proceeds to resolve normally

Nuances:

• Brynhir's effect prevents "playing" cards (taking them from a zone and putting them on the chain), but cards already on the chain as pending items will still resolve
• If opponent plays a unit and you play a damage spell from Promising Future, you can target their unit because it finalizes and resolves before your spell finalizes, making it a legal target