Esper Sentinel

Rhystic Study for one mana, on a body, in white: that reframing gets tossed around freely, but it undersells how differently this card ages. Where the blue enchantment charges a flat one-mana tax forever, this tax scales with the creature's power, which separates a real engine from a mild annoyance. Left as a 1/1 it costs opponents a single mana to ignore, an entirely reasonable price. Pump the power (equipment, an anthem, any counter) and the tax climbs with it, until paying two, three, or four to resolve an interactive spell becomes a tempo loss the opponent would rather not eat, at which point you draw. It never hard-locks anyone; it only levies a toll whose size the owner dictates, and the opponent always retains the option to pay through. Its aim is precise, too. The trigger catches only the first noncreature spell a player casts each turn, so the tax lands on the opening interaction (the removal, the ramp, the wrath setup) rather than trying to gum up an entire turn. That targeting keeps it honest and also makes it sting: it charges for the spell an opponent least wants to slow-play. That white got a taxing card-draw engine at all is notable; the color has historically bought its card advantage with bodies and enchantments, not with cheap artifact creatures that punish spellcasting. This is the rare white one-drop that reads as a resource generator before it reads as a creature.