Oaken Siren

A mana dork disguised as an evasive creature, which is a rare shape in blue. The tap ability produces exactly one color and locks it to a single purpose: artifact spells or artifact abilities, a restriction that turns this from a generic accelerator into a build-around's supporting cast. That constraint funds the rest of the package. A 1/2 flier with vigilance is not a body you usually get to attach to a ramp source, since vigilance means it commits to the air and still holds the tap open on the crackback. Blue has historically leaned on stone-cold rocks and enters-tapped fixing to power out its bigger artifacts; putting the mana on a creature that can also chip in and defend is a different bargain, trading raw efficiency for a warm body that pressures life totals while it fuels the machine. The artifact-only clause keeps it from becoming a universal blue ramp piece, which is precisely the point: it wants a deck already committed to casting artifacts, where the mana is never wasted and the flying clock is a free upside. Being an artifact creature itself folds it into the very thing it powers, so it counts toward the artifact-matters triggers it exists to enable.