When using Mystic Reversal on Icathian Rain (a spell with 6 reflexive triggers), do you steal just one trigger or the entire spell?

Ruling: You must use Mystic Reversal on the spell before it resolves and creates its reflexive triggers. If successful, you steal the entire spell, and when it resolves under your control, you create all 6 reflexive triggers.

Sequence:

• Opponent plays Icathian Rain
• You must use Mystic Reversal before they begin targeting (before the spell resolves)
• If Reversal succeeds, you gain control of the spell
• When the stolen spell resolves, you create all 6 reflexive triggers under your control

Nuances:

• You cannot Reversal individual triggers - only the spell itself before it resolves
• If the opponent has already started targeting, it's too late to use Mystic Reversal
• You can ask them to wait before targeting if they rush ahead
• Once you let them target, the window to use Reversal has passed