Captain Mar-Vell, Space-Born

Reactive white gets a proper engine here, and the condition is the whole design. Cosmic Awareness is a static ability with a continuous check: for as long as an opponent has cast a spell this turn, your spells (creatures and noncreatures alike) may be cast as though they had flash. That lets you hold up a sweeper or a threat and answer their play in kind, or wait for the end step once the coast is clear. Either way you convert their proactivity into your flexibility. The lever is dependence, and it runs in one direction: the ability only cares whether an opponent has cast a spell, never whether you have, so the payoff is yours alone while the timing sits in their hands. That asymmetry is the discipline. Against an opponent whose plan runs on activated abilities, tokens, or a stalled board that never commits a spell, the awareness simply never switches on, and the flash upgrade never arrives. Compare the unconditional enablers like Vedalken Orrery and Leyline of Anticipation, which grant the instant-speed rhythm outright and ask nothing of anyone; here you buy the same effect with a body that only opens the window when your opponent chooses to. The 4/4 flier with vigilance earns its keep in the meantime, pressing damage in the air and staying back to block, so the card holds a board even on the turns the window stays shut. That is a careful way to price a hand-wide flash effect: give it a defensible frame, then let the opponent decide when it goes live.