Spirit Shield

The interesting wrinkle here is the design's use of a tapped artifact as a persistent state, not a one-time effect. Most pump from this era was instant-speed and ephemeral: spend the mana, get the bonus until end of turn, repeat. This instead converts the artifact's own tap status into a continuous buff that lasts "for as long as this artifact remains tapped," which is why the "you may choose not to untap" clause exists at all. Without that opt-out, the toughness bonus would evaporate on your next untap step and the card would be a strictly worse pump spell. With it, you can lock the artifact down indefinitely and keep a creature at +0/+2 across multiple turns, trading the artifact's continued availability for a standing defensive boost. The cost of that design is the obvious one: a tapped Spirit Shield is a tapped Spirit Shield, so committing to one creature's toughness means you cannot reactivate the ability elsewhere until you let it untap and surrender the bonus. It is a clumsy engine by modern standards, the activation cost steep and the payoff purely defensive, but the underlying idea (an artifact whose tapped state is itself the effect, maintained at the cost of the artifact's own readiness) is a recurring design language that later cards would refine into something far cleaner.