Do you have to play Defy/Wind Wall on cards like Gust and Hextech Ray before targets are chosen (like with Falling Star), and do you still get effects like Dreaming Tree's draw if the spell is Defied?

Ruling: Most spells target when the card is added to the chain, unlike Falling Star which creates reflexive triggers on resolution (indicated by "do this" text). You can respond to these spells normally after they're played and targets are chosen.

Sequence:

• When a spell like Cleave is played targeting a unit, it's added to the chain with targets already chosen
• Dreaming Tree triggers and is added to the chain
• Opponent can respond with cards like Fight or Flight
• Chain resolves backwards (top to bottom)

Nuances:

• Falling Star is unique because it creates reflexive triggers on resolution, so you must Defy/Wind Wall it before targets are chosen
• Cards check legality on both activation and resolution, so if a target becomes illegal (e.g., Ravenbloom gains might above 3 after Gust targets it), the effect will fail on resolution
• Cards like Ravenbloom only trigger after a card has fully resolved and been played, not when cards are added to the chain