Creatures:
Delver of Secrets
: The namesake of the deck archetype, Delver is the highest value blue one-drop available. Flipping one of these on turn two feels great.
Young Pyromancer: This card has been in and out of Delver lists in various quantities, but with the amount of cheap spells in the deck, Pyromancer gives insane value starting from turn two (with a Gitaxian Probe) and compounding if left alive.
Gurmag Angler: The largest and most expensive creature in the deck, the Angler supplies a way to face down Tarmogoyfs. Super cheap come late game, and great value.
Tasigur, the Golden Fang: Not only is this card a big body for a cheap cost, his ability is amazing when you can delve away cards you don't want back.
Spells:
With 28 spells in the deck, this might take a while...
Lightning Bolt: The most played red card in the format. Your modern burn spell for killing pesky creatures or just threatening their life total.
Thought Scour: One of the best delve fuelers around. Tack a cantrip onto the end of it and this is a must run card.
Gitaxian Probe: A free spell good at any point in the game: ensuring the coast is clear for a Delver of Secrets
, getting a Young Pyromancer trigger on turn two, or late game as a cantrip and to see their hand.
Kolaghan's Command: Returns a Tasigur, the Golden Fang or Gurmag Angler that was killed or Thought Scoured, works as a partial Mind Rot, becomes an Ancient Grudge, or even a Shock. The best part is that it works at instant speed and you choose the best two options.
Mana Leak: The best cheap, easy to cast counterspell in modern. Works in 90% of all cases (besides maybe Tron).
Serum Visions: The best blue cantrip available in modern, barring a Preordain or Ponder unbanning.
Terminate: Our unconditional kill spell of choice. The casting cost can be a little tight on our mana base, but it's worth it.
Murderous Cut: for an unconditional kill spell? Sign me up! This deck can easily handle six delve cards, especially without Snapcaster Mage cutting down our graveyard.
Remand: This card is good as a tempo play, and is a great combo disruptor.
Dispel: I like the single copy of this card in the main because of its myriad of uses against basically every deck in Modern. It is extremely effective in control matchups and counter wars, it's an even trade or better with any of burn's instants, and is especially valuable in Delver mirrors.
Electrolyze: This card is extremely flexible and useful in most matchups, tagging multiple X/1s or even just cycling at the end of the turn.
Spell Snare: Arguably stronger than Dispel in the average match, Spell Snare tags important cards in all matchups, regardless of card type, in exchange for being a slightly inferior spell in combat scenarios and against combo. This card hits Scavenging Ooze, Tarmogoyf, Dark Confidant, Terminate and Grim Flayer out of Jund, Eidolon of the Great Revel and Boros Charm in Burn, as well as Remand, Snapcaster Mage and Mana Leak against control.
Anger of the Gods: Good against Burn and Zoo,
really good against Dredge, this comes in against any aggro strategy.
Countersquall: Similar to Negate, this really helps in control matchups to make it easier to burn them out.
Dismember: A , 4 life kill spell for when you really need it. Mostly for Bant Eldrazi.
Dispel: In case you need a second copy for the control or burn matchups. Also decent against Infect.
Inquisition of Kozilek: Great in the control matchup, this card is also effective against combo to strip their combo piece or slow them down.
Izzet Staticaster: Blows Lingering Souls and other token strategies out of the water.
Negate: Similar to Countersquall, this is better against burn to reduce the damage you have to take from shocklands to get it online.
Pithing Needle: The catch-all for any activated abilities, good for Affinity.
Rakdos Charm: Cheap, effective graveyard hate for Storm and Dredge.
Rough/Tumble
: A more flexible Pyroclasm. Used against aggro.
Spellskite: Decent against Infect, although they may have Twisted Image. Also great against Bogles and Burn.
Vampiric Link: For the Burn matchup. Stick one of these onto a Eidolon of the Great Revel to gain life whenever its ability triggers.