Aysen Highway

Landwalk as a color-wide payoff is the design idea here, and the steep triple-white cost tells you how much Wizards distrusted it. Most landwalk in the game is creature-bound: a single attacker with islandwalk or swampwalk that the printing deliberately limits to one body. This pours the keyword over an entire color at once, granting plainswalk to every white creature on the battlefield the moment a defending player keeps a Plains in play. It is symmetrical by the letter, so a white mirror hands evasion to both sides; but in a deck built to attack, the side with the wider white board is the one that cashes the keyword in. The effect is fragile by construction (a defending player who never controls a Plains shuts the whole thing off), and that conditional is the pressure valve that lets the ability span a color rather than a single creature. In practice it bets that white-leaning metagames are common enough to matter, a bet that ages poorly the more nonbasic and fixing the format offers. The six mana, weighted into three white pips, is the rest of the brake: by the time you assemble it, you are deep into a board state where you would rather be deploying threats than enchanting them with a situational evasion blanket. It reads as an artifact of an era when "all white creatures gain a keyword" was treated as a high-cost, color-defining reward, and when landwalk was a load-bearing mechanic rather than a vestigial one.