Does Possibility Storm affect spells cast from zones other than hand?

Possibility Storm reads: 'Whenever a player casts a spell from their hand, exile it...' — wait, actually it reads 'Whenever a player casts a spell from their hand.' This is a critical detail: the Oracle text of Possibility Storm specifically says 'from their hand.' So it only triggers when a spell is cast from the hand, not from other zones like exile or graveyard.

Under CR 603.1 and 603.2, triggered abilities only trigger when their specific trigger condition is met. Since Possibility Storm's condition is casting a spell 'from their hand,' casting a spell from exile (e.g., via Flashback, Suspend, or cascade) does not trigger Possibility Storm.

This means abilities like Flashback (casting from graveyard, CR 702.34), Cascade (casting from exile, CR 702.84), or any other alternative zone casting will not cause Possibility Storm to trigger, because the spell was not cast from the hand.

Example: Your opponent has Possibility Storm in play. You cast Ancestral Vision from exile via its Suspend ability (CR 702.61). Possibility Storm does not trigger because the spell was cast from exile, not from your hand.

So the answer is: Possibility Storm only affects spells cast specifically from the hand. Spells cast from any other zone are unaffected by it.