Extended Oath deck
Oath of Druids, sometimes just simply Oath, is a blue, green and white combo-control deck. Hiding behind a large amount of countermagic, the deck would use Brainstorm, Impulse and Enlightened Tutor to find the namesake Oath of Druids. The Oath in return would bring either a utility creature such as Spike Feeder or Shard Phoenix into play or a big finishing creature such as Morphling. Meanwhile, Gaea's Blessing would make sure that Oath wouldn't kill the player and also enabled to shuffle the utility creatures which could be sacrificed or otherwise killed on their own back into the library to be found by Oath again. The same could be done if the finishing creature would be killed.
If the opponent refused to play creatures, manlands like Mishra's Factory or Treetop Village could be used to continuously attack the opponent.
Since the deck already utilized card search and Enlightened Tutor it was also easy to enlist a silver bullet approach utilizing single copies of artifacts and enchantments which could heavily disrupt the opponent's gameplan. Creatures could also be used for this since they could be searched for by Oath. With this silver bullet plan, the sideboard of the deck was usually also mostly single copies of cards.
The Oath of Druids archetype grew in response to the metagame in early 1999. Memory Jar and High Tide were the decks that were dominating the Extended PTQs during winter of 1998-1999, known as Combo-Winter. From the playgroups of the University of Illinois, Mike Stuller suggested using Oath of Druids for creature control along with the Enlightened Tutor Silver Bullet concept. The deck was used by Ped Bun when he tragically lost the final of a Pro Tour Qualifier by mistaking a Brainstorm for a Impulse and was given a game loss for looking at extra cards. However, it inspired Bob Maher to use this deck who went on to place in the Top 8 of Grand Prix Kansas City in March of 1999. In December of 1999, Maher won Pro Tour Chicago with the deck followed up a month and a half later by winning Grand Prix Seattle 2000.
In 2008, Mike Flores called the Pro Tour winning deck the 7th most powerful Extended deck of All Time. [1]
When Weatherlight left the format and with it Gaea's Blessing, it was replaced by Krosan Reclamation and Cognivore became the finisher of choice. However, the deck had lost most of its original silver bullet approach in the meantime and was primarily a blue-green control deck which at times splashed black for Pernicious Deed. However, Oath of Druids and Living Wish still enabled the deck to play a large variety of creatures depending on the game situation and opponent. Justin Gary won Pro Tour Houston 2002 with such a changed Oath deck.
Turbo-Land
Zvi Mowshowitz designed a new Oath variant called Turbo-Land during the time Oath was a popular deck. While keeping Oath of Druids and utility creatures as well as the large amount of countermagic, it replaced the silver bullet approach with a combo. The deck would set up a card draw engine by combining Horn of Greed with Exploration while Gush was also played for big card draw and replaying lands to draw even more cards from the Horn. This would be repeated until the library was empty. At this point there should be enough lands in play to cast Time Warp and Gaea's Blessing targeting the Warp and another copy of Blessing. This would give the deck infinite successive turns by repeating it every turn.
When Weatherlight left the format, this deck also replaced Gaea's Blessing with Krosan Reclamation. However, the deck had also gained Battlefield Scrounger which could easily set up the Time Warp combo. With the large amount of mana since the deck had practically all it's lands in play, it was also capable to cast Capsize with Buyback every turn to clear the board when it it hand infinite turns and finish the game with manlands and Scrounger.
Mowshowitz won Grand Prix New Orleans 2003 with a Scrounger based Turbo-land.
Demise
While Oath of Druids based decks had a decent showing during Pro Tour New Orleans 2003, the format was dominated by artifact based combo decks in the wake of the release of Mirrodin. Practically every game during the entire tournament was decided in four turns or less. Following this, Wizards of the Coast had decided to slow down the format and and ban a lot of cheap combo enabling cards, one of which being Oath of Druids.[2]