En 4e édition (mai 1995, cf. extrait du livret de règles) et même en revised (avril 1994, cf. article) il y a des références aux points de vie négatifs. En alpha / beta, le
rule book originel ne parle pas de points de vie négatifs. Du coup, ère glacière c'est juin 1995, donc ça avait été clarifié bien avant, et pas spécifiquement pour sortie de
Zuran Orb.
Winning
If, at the end of any phase of either player's turn or at the beginning or end of an attack, your opponent's life total is 0 or less, you win. If a player's life total reaches 0 or less at any other time, that player has until the end of the phase to get back to 1 or more life. If both players are reduced to 0 or less life during the same phase (even one player is at zero and the other is at -100), the duel is a draw and both players keep their ante. If you can't draw a card when required to do so, you lose the duel immediately. Certain cards may define other ways to win or lose.
Few readers are probably aware of this, but the idea of dying at the end of the phase actually originates with Revised Edition, not First Edition. Although either silent or ambiguous under the First Edition (Alpha/Beta) rules, the Revised Edition rulebook changed or clarified a critical point regarding when games are won or lost: “If your opponent’s life point total drops below 1 at the end of a phase or at the start or end of an attack, you win.” In other words, you did not simply lose the game for having 0 life. You could play spells, pool mana, use fast effects all with zero or even negative life. You only died at the end of a phase for having zero life.