Fluxcharger

A 1/5 flyer is a wall that leaves the ground, and on its own that is a fine body to hide behind: it blocks nearly anything in the air, walks through small attackers untouched, and shrugs off most early removal. The switch is what turns that static line into a clock. Every instant or sorcery flips it to a 5/1, which moves the math onto the combat step rather than the stack: cast on your own turn, swing for five in the air, and the toughness reverts at end of turn. That window is real but exposed; on the turn the 5/1 attacks, a single point of damage from instant-speed removal or a small flyer or reach blocker erases it, so the evasion is doing more work to keep it out of harm's way than the toughness reset is. The optionality matters, because the trigger is a "may," not a forced swap; you keep the 1/5 when you need the blocker and reach for the 5/1 only when the damage lands. That makes it a deck-dependent payoff: a passive flyer in a creature deck, a recurring five-power evasive threat in one that fires off two or three spells a turn. It sits in the spell-matters tradition of rewarding noncreature density with a body that scales by how hard you lean on instants and sorceries, paying out in evasive damage rather than counters or card draw, and only on a turn you have a spell to spend.