Githzerai Monk

The trick isn't the flyer; it's the phase you cast it in. Flash plus a mass-tap on entry means the reactive line is to cast this during your opponent's beginning of combat step, before attackers are declared: tapped creatures cannot be declared as attackers, so the swing never happens. Timing is everything, because tapping an already-attacking creature does nothing to remove it from combat. The window is narrow and specific, and playing it correctly means holding priority in the pre-declaration step rather than waiting for the attack. Call it a defensive Fog that leaves a body behind, but the tap is broader than pure defense: because it hits every creature you don't control, it can also strip blockers off a board you intend to swing into, opening a stalled ground the turn after. The one-shot enters trigger is the constraint that keeps five mana honest; this buys one clean turn of tempo, not a repeatable lock. The part that earns the extra mana over a plain Fog is the flying threat that stays behind to press whatever advantage the tap just created, so the mana isn't spent purely on denial. Note also that tapping isn't neutralizing: creatures with instant-speed activated abilities or ways to untap can still do work, and anything already committed elsewhere is unaffected. Built for the white player who wants combat interaction that stays on the field afterward as a clock.