Delver of Secrets
The namesake of the deck, and the reason why the deck is so explosive.
Young Pyromancer One of the best threats in the deck. It can take over the game quickly if unanswered. Getting a Pyromancer out with a few cantrips also helps stabilize your defense against opposing ground forces, or go wide and swarm the opponent.
Tasigur, the Golden Fang The black 'Goyf that draws cards and can cost 1 mana. The fact that it's legendary is the only drawback. This is the card that made Grixis Delver competitive.
Snapcaster Mage Arguably the best blue card in Modern. The deck uses it's graveyard a lot so this may not always have a lot of options available, but it's so useful.
Lightning Bolt One of the best red cards in the format, possibly the entire game. Kills stuff or goes to the face.
Serum Visions This is the best Modern has to offer in terms of cantrips.
Gitaxian Probe Gives you information and cantrips for just 2 life. Fills your yard, spawns elementals, lets you prioritize counters.
Thought Scour This card allows for turn two a Tasigur. It is however disappointing to draw more than 1, or draw them late game.
Murderous Cut The main reason to play black. It kills a creature at instant speed for potentially 1 mana.
Terminate Kills anything for .
Smother Kills anything under 3 cmc for . It's legit.
Electrolyze Burns the opponent, kills creatures, and draws cards. It's always card advantage, which is want this deck wants.
Kolaghan's Command Everytime this card is cast, it's a 2-for-1. Two damage kills a lot things, returning a dude is always good, there are a lot of artifacts in modern, and discard is usually good. It gets even better when flashed back with Snapcaster.
Mana Leak It's really good in the early game, but looses a lot of value in the late game.
Remand It generates so much tempo. It's a cliche, but often times this card acts as a Time Walk.
Spell Pierce It counters noncreatures in the early game, and can go unexpected game one.
Spell Snare It hits 2 drops. That's a lot of impactful spells in modern. 'Goyfs, most of burn's spells, opposing counterspells, Bob, etc..
I will not play Thoughtseize / Inquisition of Kozilek / Duress for the following reasons:
1) These force you to commit to black very early in the game. You are either forced to grab an early swamp and risk not having enough red/blue mana, or commit suicide setting up your mana.
2) These greatly decrease in value as the game grows longer and both players start to run out of cards.
3) The life loss from TS is not negligible. There is no way to gain back that life. Unlike Junk, we do not have access to life gain to stabilize.
4) These are not good for tempo. You spend 1 mana to remove a card that they haven't devoted resources to.
5) Discard generally leads to top deck wars. We are not favored in top deck wars.
