-Esper Charm is the namesake card of the deck. It is a Divination, Mind Rot or a Demystify on a single spell and at instant speed. Most of the time you will use it to gain raw card advantage, but sometimes, mind rotting an opponent at the right moment can be devastating. It forces instant speed spells to come out when you choose and other times it makes them discard threats that could possibly make them win.
-Cryptic Command is the most powerful counterspell in the modern format for its flexibility. It can tempo your opponent out with the bounce mode and timewalking creature decks with the tap all creature mode. It is also possible to return your own Snapcaster Mage to your hand for extra value. It can permanently answer threats by countering spells. The only downside is that it can clutter your opening hand.
-Opt may not go as deep as Serum Visions does, but it makes cards like Spell Snare and Snapcaster Mage way better. When on the draw, it might be hard to make the decision to Serum Visions or leave a Spell Snare up, but with an Opt in hand instead of a Serum Visions, there is no need to bother.
-Spell Snare is amazing against midrange decks, blue mirrors and affinity because it can effectively hard counter a 2 mana play like Tarmogoyf or most counterspells in the format for a single mana. Opt makes this card a tad bit better.
-Negate is amazing against a lot of the threats in the current metagame, like Karn Liberated, Scapeshift, Ad Nauseam or Collected Company. It is also very good at protecting our creatures against spot removal and wrath effects. Depending on the format, Logic Knot might be worth considering.
-Think Twice is another source of raw card advantage to help you make your land drops and is an alternative to Esper Charm when used to Mind Rot an opponent. It is also very good when facing a Liliana of the Veil as an answer to her +1.
-Sphinx's Revelation is most of the time a game ender when cast for X=4 or 5. It gains you life against aggro decks and let's you find more answers against your opponent's threats.
-Path to Exile is the best removal in the format and it unconditionally kills most creatures in the format for good. The extra land is most of the time irrelevant against our deck.
-Fatal Push is also an amazing spot removal that can kill most creatures in the format. It works best with fetchlands and is played over wrath effects because we run more creatures than usual.