For Icathian Rain (and similar cards that say 'do this X times'), do all targets need to be named when the spell hits the chain, or does the player declare targets one by one as each instance resolves?

Ruling: When a spell like Icathian Rain resolves, all targets must be declared at once as the individual damage instances are placed on the chain. Players can then react between each damage instance as they resolve one by one.

Sequence:

• Icathian Rain is played and hits the chain
• Players can react to the spell itself (this is when you could counter it)
• Rain resolves and creates 6 separate damage triggers on the chain
• All 6 targets must be named at this point when the triggers are placed on the chain
• Players can now react before each individual damage trigger resolves
• Each damage trigger resolves one at a time, with reaction windows between each

Nuances:

• You cannot counter the individual damage triggers, only the original spell before it resolves
• Opponents know all targets before the first damage resolves, so they can make informed decisions about when to react
• This matters for cards like Zhonya's - you can let some units die first, then reveal Zhonya's before a specific damage trigger resolves to save that unit
• There's usually little strategic reason to react between triggers rather than immediately after targets are declared, but the option exists