Mono-Blue Delver
"So what are you playing?"
"The meta wrecker. The format killer. The little engine that could. The 17 land control deck. The ultimate hybrid of constructed formats. The-"
"Okay, okay. I get it. Mountain, tap, suspend Rift Bolt."
"....Dang."
[Edit as of 4/6/18 - Tweaked the numbers on sideboard cards and added some new meta stuff. Fixed the land count. Cut Brainstorm for more Ponder and Preordain.)
Pauper is cheap. You could buy, for the price a single Modern deck (the average price running around 600-700 dollars) the twelve most played decks in Pauper. Decks commonly run at around $50, and if you own Magic cards, you probably own a significant number of format staples. If you want to only spend $13, you can do that too (look up "14 Swamp Black").
Each time a new set or expansion is released, Pauper gains a massive influx of cards, meaning that deck innovation is very much alive in the format. Pauper even gains new cards from reprints that reduce card rarity (like the now-banned Peregrine Drake). This isn't to say that the metagame is insanely flexible or that your deck will be rendered obsolete by new cards: every single archetype has a home in Pauper, from grindy 5-color control lists like Tron, to efficient, explosive aggro like Stompy. And if you like to play tempo... look at the rest of this primer.
Decks are competitive, but the format is very heavy on interaction, and turn four kills are extremely rare. This isn't to say that Pauper isn't fast, of course. Just that there is a small and important banlist that keeps things from getting too fast. Cranial Plating, Empty the Warrens, Grapeshot, Cloud of Faeries, Cloudpost, Frantic Search, Invigorate, Treasure Cruise, Temporal Fissure and Peregrine Drake are banned.
Mono-Blue Delver, or just Delver for short (there are many different builds of the deck, but they all evolved later in the format's history and often don't have the raw power of the strictly blue build), is a tempo deck for Pauper. The deck aims to play a series of powerful, aggressive threats early in the game, and then protect those threats with countermagic, all while cantripping into more cards. This gameplan has proved to be incredibly reliable and fast, and the deck is considered one of the top-tier powers in the Pauper metagame.
Delver rewards both skill and tuning, and although the core of the deck usually remains the same, many pilots revise and update their lists often. Learning how to play the deck, however, is often more important than meta knowledge (which is still crucial to winning, obviously). The decision trees of the deck can be extremely important, and sequencing spells is often tricky.
Delver of Secrets
: The best tempo creature ever printed. With the amount of noncreature spells and cantrips our deck runs, this will almost always flip the turn after it's played, leaving opponents under a serious clock. Delver's 3/2 body also trades with just about
everything in Pauper. Scary as heck to sit across from, and dominant in
every single format where it is legal (except Vintage, where it is still present, but not tier 1).
Faerie Miscreant: First off, it's a 1/1 flyer for , which is okay in itself. Second, it's a faerie, so it has synergy with Spellstutter Sprite. Third, it sometimes cantrips, and can also be picked up with Ninja of the Deep Hours to do so again. This card oozes synergy, and I really like it.
Ninja of the Deep Hours: One of the best ways to get ahead on card advantage that we have. While its 2/2 body isn't all that great, its passive ability generates constant CA or forces opponents to hold back blockers. This card is almost never cast for its regular cost, and its ninjutsu cost often gives you the ability re-use value creatures like Spellstutter Sprite or Pestermite.
Pestermite: An evasive, aggressive creature with flash, that gains a little tempo when you play it. I really like this card, but it could easily be replaced by something else.
Spellstutter Sprite: Counters dozens of commonly played cards
by itself, and dozens more with other faeries on the battlefield. It can also be flashed in against a tapped-out board so that you can ninjutsu in a Ninja of the Deep Hours.
Spire Golem: Often a 2/4 flyer for as little as 2 mana, sometimes played for one mana or even for free. This card is a variable inclusion in some lists, and is often replaced with something like Phantasmal Bear (aggro focused versions) or Man-o'-War (pure tempo versions). Overall, a big, evasive threat.
Counterspell: An automatic inclusion in almost any mono-blue deck, especially in one that relies on fast, unprotected threats.
Daze: Acts as a more expensive Force Spike (which was already a good card), but also surprises a huge number of opponents. Stupidly good.
Deprive: Counterspell 5-8. Bouncing a land actually does matter some of the time, so I only run one.
Gush: Gush is banned in Legacy (mostly because of its interaction with Brainstorm, but still). For a long time, Gush was restricted in Vintage, for good reason. Gush draws you two cards for no mana. Gush can sometimes generate extra mana. It's not a format-breaker in Pauper, but it is very, very good.
Memory Lapse: Acts as a pseudo-Remand, gaining you tempo while taking it from your opponent.
Preordain: Scries and then draws, just like a cantrip should (ahem). Incredibly solid, incredibly powerful.
Snap: Bounces creatures, allowing you to attack or simply gaining tempo. Then the real fun starts. Untapping two lands means that Snap has functionally no mana cost. You can hold up Counterspell and then counter the creature. You can chain Snaps. The possibilities are (non-literally) endless.
Vapor Snag: Bounces a creature, pings the opponent. Just surprisingly good.
Island: Nothing fancy here. Just good old fashioned basics.
Curse of Chains: Saves you from Gurmag Angler, Fangren Marauder, Ulamog's Crusher... basically, this comes in against big scary stuff that we can't beat. A little obsolete in the current meta.
Dispel: Counters... so many things.
Echoing Truth: Swings tempo in your favor, and destroys token-based decks.
Hydroblast: Against anything red, this is fantastic.
Piracy Charm: Value and utility in a one-mana package.
Stormbound Geist: Pure value. Gives the deck an edge in grindy matches.
Bonesplitter: Increases our clock massively against control.
Gut Shot: Absurd in the mirror and against Elves.