Modern Faeries deck
Faeries is an Aggro-control deck for the modern format. The deck has its roots in Lorwyn block and the Standard environment in which the block was legal, making use of the Faerie tribe which was present in the block, combined with control cards like Thoughtseize and Cryptic Command. Luis Scott-Vargas played this deck quite often during the standard season that it was legal. The deck is usually Blue and black, e.g. Standard U/b Faeries deck, but other variants have also been of note, particularly the mono-blue version.
Blue-Black Faeries
While the deck has a considerable amount of flex spots that will shift with the meta, there is a basic formula that most decks employ. A suite of hand destruction spells in the form of Thoughtseize and Inquisition of Kozilek, a suite of counterspells usually revolving around Cryptic Command and other counters like Mana Leak or Remand, a selection of supporting blue faeries that can be used in concert with Bitterblossom to maximize its effect, and lastly a suite of kill spells which vary greatly from Smother to Dismember.
The UB variant can take two strategies as the game progresses. Either resolving an early Bitterblossom and protecting it allowing the pilot to ride the Faeries to victory or generating a considerable amount of tempo with flash creatures, particularly in the form of Spellstutter Sprite and Mistbind Clique which will allow the pilot to press advantages while disrupting their turns at inconvenient times.
A notable fixture of the UB (and the mono-blue) list is the painless mana base. This is counter-intuitive to the normal fetch land mainstays of the format. The strength of this color combination in Faeries is the existence of Secluded Glen. Most of the time, it will function as an Underground Sea giving access to untapped blue and black mana on any turn of the game. River of Tears is a unique land that feels like it was printed for this deck. All important black spells usually need to be cast at sorcery speed and conveniently almost the only time River of Tears produces black mana is on one's turn. At all other times and most importantly on the opponent's turn, the land produces blue mana allowing the pilot to leave open countermagic. Because of the existence of these lands, there is no reason to use the resource that is the life total for anything other than producing faeries and taking important cards out of the opponent's hand.
There is a considerable amount of debate in the Faerie community about the viability of Scion of Oona in the deck. Most agree that either zero or four copies should be included in the list. The card is powerful as it gives a way to push through a lot of damage at instant speed but including it makes the deck very weak to spot removal pushing more conservative players to cut it for more control elements in their list. The card is often included in the mono-blue list as a way to turn all important faeries into more considerable threats. Its inclusion or lack thereof is usually a personal choice about the type of deck and the meta of the immediate play area.
Mono-Blue Faeries
The Mono-Blue Faeries list has a few notable strengths that set it apart from its UB counterpart. The first is the mana base which is almost entirely basic land cards. While UB Faeries is susceptible to Blood Moon in the worst way, the mono-blue variant cares very little about it. The other strength is the expanded counter-magic suite. It is conceivable for this variant to simply not allow the opponent to ever resolve a spell, especially on the play. It has ahead-of-the-curve counter spells for every spot on the mana curve. Additionally, the inclusion of Vedalken Shackles can effectively shut down any creature-based plan that might be used against it.
The weakness of playing this variant is the absence of Bitterblossom which considerably powers down Spellstutter Sprite and Mistbind Clique. However, this version is almost entirely a tempo-generating aggro-control strategy with little wiggle room. Once the plan is either disrupted or the pilot stumbles even a little bit, chances of losing the game skyrocket to an almost insurmountable degree. This can be hedged against with the inclusion of board resets in the form of Hibernation, Hurkyl's Recall, and main boarding Vapor Snag. However, these sorts of strategies do weaken consistency. Ultimately, there is a unique balance that must be mastered and understood when piloting this deck.