Welkin Tern

The 2/1 flier with a defensive ceiling: it patrols the air and nothing else. The downside clause is the whole transaction. A vanilla 2/1 flier for two mana would be a quietly excellent rate, the kind of evasive aggressor blue rarely gets at this cost, so the inability to block ground creatures is the tax that pays for the body. The result is a creature that only ever does one job well, which is to attack, and offers nothing on the turns you need a wall. That single-mindedness is exactly the point. It is built for the tempo deck that wants its two-drop applying pressure in the air every turn while the pilot holds up countermagic or bounce, never for the controlling shell that might want a blocker. The asymmetry rewards the aggressor and punishes the hoarder: keep it attacking and it is overcosted by nothing; sit back with it and you are holding a creature that cannot even trade with the ground threats coming at you. Blue has a long line of these efficient-but-fragile evasive bodies whose drawbacks are deliberately built to discourage a passive game; this is among the cleanest statements of that design, all upside on the offense and a brick on defense.