Aeromoeba

A 2/4 flyer that blocks all day is a fine body; a 4/2 flyer that trades in the air and races is a different animal, and this card lets you flip between the two by paying a card. The activated ability costs no mana, so the switch is always available: a defensive posture during your opponent's turn, an aggressive one during yours, adjustable in response to a pump spell or a combat-trick threat on the stack. What makes the design cohere is the discard cost, which prices the flexibility in the one resource a control shell is happiest spending: cards it wanted in the graveyard anyway. That pushes the beast toward decks built around discard-as-fuel, where feeding a flashback spell, a delve payment, or a threshold count doubles as combat manipulation. Read straight, the power/toughness swap is a small trick; read as an engine piece, it turns each turn's card economy into repeatable, mana-free rate adjustment on a resilient blue evasive body.