Arboria

The design is a pacifism clause turned into a table-wide social contract: combat is gated on activity, and the player who sits still is the player nobody can swing at. World enchantment status means only one Arboria exists at a time, the era's solution to the obvious problem of stacking lockout effects into something unbreakable. The clever piece is what counts as "activity": casting a spell or landing a nontoken permanent on your previous turn opens you up to attacks, so the static restriction punishes the engaged player and shelters the one drawing-go. That inversion is what makes Arboria more than a fog. It rewards a specific shape of play (hold up answers, deploy nothing, let opponents fight each other) and creates a genuine prisoner's dilemma at multiplayer tables, where breaking the peace to develop your board is the same action that makes you the legal target. The Legends design team was working through a lot of these multiplayer-political ideas in green and white, and Arboria is one of the cleaner expressions: a deterrent rather than a prohibition, with the opt-out written directly into the attack restriction itself. Token generation slipping past the clause is a small accident of templating that later designers would have closed; in 1994 it was simply how nontoken got written.