Instill Energy

Granting attacks the turn a creature comes down was novel enough in early Magic that the rules text had to spell it out longhand, and the modern Oracle wording ("can attack as though it had haste") is deliberately narrower than full haste: the enchanted creature can swing immediately but cannot tap for an ability on its first turn, which is the line that keeps the aura from being a free turn-one mana or damage engine. The free untap is the part that gives the card its second life. Pairing it with a creature that taps for mana hands you a one-sided ramp loop a decade before anyone had a name for that pattern; pairing it with a tap-to-deal-damage creature gives you a repeatable pinger you can fire twice a turn. That untap also reads now as a primitive vigilance substitute, letting an attacker stay open as a blocker. The reason this aura rewards reading now is how much it bundled into one slot: haste, an untap, and a vigilance-adjacent mode that later sets would parcel out one card at a time. Haste became a keyword; green got vigilance on bodies; the untap line resurfaced piecemeal on cards like Quirion Ranger and Seeker of Skybreak. Reading the aura now is reading a single piece of cardboard doing the work that the rules vocabulary later split across half a dozen.