Do spells like Icathian Rain need their targets declared when added to the chain, or when they resolve?

Ruling: Icathian Rain does not determine targets when played/finalized. When it resolves, it creates 6 reflexive triggers (new abilities) that are added to the chain as Pending, and targets are declared for these triggers during the ensuing cleanup after Icathian Rain finishes resolving.

Sequence:

• Icathian Rain is played and added to the chain (no targets declared yet)
• Players can react to Icathian Rain being played
• Icathian Rain resolves and creates 6 new triggers/abilities as Pending
• During cleanup, these 6 triggers are finalized and targets must be declared for all 6
• All 6 triggers are added to the chain as individual chain items
• Players can now react to each of the 6 individual triggers, starting with the last one added
• Each trigger resolves individually, dealing 2 damage to its target

Nuances:

• You can react to Icathian Rain being played, but targets aren't chosen until it resolves
• All 6 triggers must be added if any can be added - you cannot stop partway through
• You must target your own units if there aren't enough valid targets elsewhere
• You can stack all 6 triggers on the same unit if desired
• Each of the 6 triggers can be reacted to separately and will pay additional costs separately (like for Deflect)
• Damage is not dealt until each individual trigger resolves, not when all targets are declared