Peregrine Drake

The five-mana cost is theater. Untapping up to five lands on the way in means the body costs whatever the difference between its mana value and your untapped lands works out to, and in the right shell that difference is zero or negative. This is a creature that pays for itself the instant it resolves, and it pays again every time it leaves and re-enters the battlefield. Therein lies the danger: a self-funding flicker target turns any free-or-cheap blink effect into a mana engine, and once your blink loop produces more mana than it costs, the loop is infinite. Wizards has printed the same untap-on-entry trick across a small family (Great Whale and Cloud of Faeries among them, the latter eventually banned in older formats for exactly this kind of free-resource math), but the Drake is the one that became shorthand for the whole pattern. Its design lesson is durable: a card that refunds its own cost is not a fair card with an upside, it is a combo piece waiting for a partner that bounces or blinks it cheaply. The flying 2/3 is almost an apology, a fair-looking front on a card whose entire reason for existing is the line of text underneath it.