When Icathian Rain is played with multiple Stalwart Poros on both sides of the field, which units die?

Ruling: What dies depends entirely on what the player targets. Icathian Rain can have multiple triggers directed to the same unit.

Sequence:

• All triggers go on the chain together
• Triggers resolve one at a time
• If a trigger's target is gone when it resolves, that trigger does nothing

Nuances:

• Unlike combat damage (which must be assigned to exactly lethal), spell damage has no such concept - you can assign all triggers to one target