Maelstrom Trickster

As Maelstrom Trickster enters the battlefield,
choose one —
• An opponent has drawn X cards.
• An opponent has cast X spells.
• An opponent has attacked with X creatures.
As long as the chosen condition has been met
this turn, where X is 2 or greater, the next spell
you cast this turn costs {x} less to cast and can be
cast as though it had flash.