How does Possibility storm work with Cascade? I need to know for Yidris chaos shenanigans
When you cast a spell with Cascade from your hand, both the cascade trigger and Possibility Storm’s trigger happen. If you control Possibility Storm, then you choose the order in which the triggers go on the stack. If you don’t control Possibility Storm, then the order of the triggers depends on whose turn it is. (If it’s your turn, then Possibility Storm’s trigger will go on the stack above the cascade trigger.) The order of the triggers doesn’t matter, however, since the net result won’t change.
If the Cascade trigger resolves first, then you’ll cascade normally and then do Possibility Storm’s effect normally.
If Possibility Storm’s trigger resolves first, its effect resolves normally. When the cascade trigger goes to resolve, it still knows the CMC of the spell it triggered off of and will use that information to determing the CMC of spell that it will cascade into.
Possibility Storm doesn’t trigger for the free spell off of a cascade trigger because the free spell wasn’t cast from a player’s hand.