Swords to Plowshares has always been the best and most efficient removal spell in the game. Period. Unmatched for the games entire 25-year history of Magic, it has in no small way defined every format it has been legal in and has in many ways dictated which archetypes and which creatures were viable. And it is also my favorite card from Masters 25.
The card's flavor originated from an ancient Hebrew prophecy of a future time in which all of humanity will cease learning war and will "beat their swords into plowshares," suggesting that humans will instead focus their efforts on growing food to sustain their neighbor rather than building weapons to use against their neighbor. This flavor played perfectly into Magic's original highly esoteric theme that drew heavily from prominent literary sources. By casting Swords to Plowshares on a creature, you would remove it from the game rather than killing it. This rendered the creature unable to engage in combat any longer, yet without sending it to the graveyard. The idea, I believe, was that the creature lived on in a place outside of the realm of war and was no longer under the sway of the planeswalker who summoned the creature onto the battlefield to do their bidding. You were essentially saving the creature from its controller by removing it from the battlefield (and also from its likely death).
In terms of gameplay, the card can efficiently take care of nearly any creature in the game, for just one mana. The drawback is that the opponent gains some life. This is usually a small drawback, especially compared to the low investment required to cast Swords to Plowshares. Sometimes it is even a bonus when you need to target your own creature to gain some life, especially in response to an opposing Control Magic or in the face of a lethal Drain Life or Fireball. It didn't take long for people to catch on to the power of Swords to Plowshares, and it likewise did not take long for it to rise to the top of the standings, helping to propel the game's very first World Champion to victory in 1994 on the back of four copies of the cards in their main deck.
In a metagame filled with Kird Apes, Serendib Efreet and Erhnam Djinns, Swords to Plowshares did some heavy lifting in Zak Dolan's path to victory at the first Magic: The Gathering World Championship. Back then they called in Type I, but nowadays we call it Vintage. At the time, there wasn't much "vintage" about the newly released game, but as we approach the game's 25th year, it seems the opposite is now true. A unique feature about Dolan's list is that he did not play any copies of Land Tax. Instead he played a copy of Control Magic and two copies of Old Man of the Sea, preferring to go the route of creature theft instead of taxation.
As Magic continued and the competitive community began to really understand card evaluations, the "control" archetype streamlined into "The Deck" by Brian Weissman.
The idea was to take advantage of all the most powerful cards in the game, including most of the cards that were restricted to one copy per deck. Instead of posing a fast threat, such as a lethal Channel plus Fireball combo or a Kird Ape backed by a Serendib Efreet, control decks used reactive cards such as Swords to Plowshares and Counterspell to prolong the game to the point where they could establish inevitability with cards like Moat, Braingeyser, Disrupting Scepter and Jayemdae Tome. Swords to Plowshares was such a powerful card that eventually decks looked to use the Mirror Universe plus City of Brass combo to kill the opponent instead of trying to win with creatures. Somehow it never managed to find its way onto the restricted list, despite its tremendous impact on the game.
As much play as creatures saw in Vintage, they saw even more play in what was known as Type II, which we now call Standard. The finals of Pro Tour New York featured two decks that each used four copies of Swords to Plowshares, but for very different ends.
Bertrand Lestrée would use the powerful instant to get rid of opposing Llanowar Elves and Birds of Paradise or whatever creature the opponent could summon before Bertrand could resolve Armageddon to reset everyone's mana. Bertrand would then use the creatures he had on the battlefield, in addition to his own Elves, to gain a big tempo advantage over the opponent, including using Strip Mine to kill future lands from the opponent or Icy Manipulator to tap them down on the opponent's upkeep.
His opponent in the finals won the tournament with a strategy much like the Mirror Universe one employed in Vintage, which sidestepped Swords to Plowshares altogether by instead winning by decking the opponent with Millstone while using Swords to Plowshares and Wrath of God backed by Counterspells to keep the opponent's creatures under control. He even chose Blinking Spirit as his only creature since it was one of the few creatures in the game that could not be killed by Swords to Plowshares. Keep in mind that at this tournament competitors were required to play with at least five copies of cards from each legal expansion, including Fallen Empires and Homelands, which made for some interesting card choices in deck building.
Swords to Plowshares continued to be one of the defining cards of Standard throughout its life in the format. The White-Blue Control archetype lived on and became a deck that used Kjeldoran Outpost as its win condition once Alliances was released. It also had Soldevi Digger as the backup plan to keep from getting decked and Thawing Glaciers to ensure that it would add a land to the battlefield each turn but also while slowly amassing card advantage.
By this time, everyone knew Swords to Plowshares was the best creature removal spell in the game. Much like Loconto's strategy to play Blinking Spirit as the only creature, Worlds 1997 runner-up Janosch Kuhn used Frenetic Efreet and Wildfire Emissary as his only creatures, a pair recently printed in Mirage that could not so easily be removed from the game (aka exiled) by the plow.
Standard and Vintage weren't the only formats where Swords to Plowshares warped the format in terms of which creatures and strategies were viable. In Extended (what is now essentially Modern), one of the game's top players, Randy Buehler, won the world's premier Extended tournament with a deck built around the Land Tax + Scroll Rack combo.
Land Tax would allow the deck to find three lands per turn, which it could then cash in for cards from the top of the library with Scroll Rack and then go find again the following turn with Land Tax. Swords to Plowshares again played right into the deck's strategy by eliminating virtually any threat the opponent could play without forcing the controlling of the deck to get out from underneath Land Tax since the removal spell only costs one mana. He also had burn spells to help deal with opposing creatures or to burn out the opponent. And he had Suleiman's Legacy to deal with all the aforementioned Djinns and Efreets.
Speaking of Legacy, Suleiman's wasn't the only one enabling Swords to Plowshares to shine. Legacy as a format, which at the time was called Type 1.5, was basically Vintage except all the restricted cards instead were banned. Swords to Plowshares was a defining card throughout the format's entire existence. As the card pool expanded, White-Blue Control decks evolved into decks built around gaining card advantage via forcing the opponent to break their Standstill.
This deck was the precursor to Miracles, and it was the deck to beat when I was getting back into Magic in 2006. In response to the prevalence of this archetype, I built a white deck with Aether Vial as its way to deploy threats without having to break the opponent's Standstill. Little did I know at the time that 12 years later I would still be playing that same archetype, albeit now for different reasons, but continuing to take advantage of the unmatched power and versatile of the most efficient removal spell ever printed.
Whether playing a control deck or an aggressive deck, Swords to Plowshares has always been the best choice. It has had such an immense impact on every format it is legal in that the best decks were often the ones that could minimize its effectiveness against them. While its days in Standard have long become an artifact of the past, and it unfortunately never had a chance to be legal in Modern, it continues to be a mainstay in Vintage and Legacy. With its printing in Masters 25, I look forward to playing with it in the new draft format. Perhaps I'll finally get a chance to play with it in a Pro Tour too as Legacy is one of the three formats in the Pro Tour's 25th Anniversary in Minneapolis later this year. This is something I'm very much looking forward to as it is my single favorite Magic card ever printed.