Current Inclusions
Abrade: A very flexible removal spell, abrade deals with any artifact and many of the most obnoxious creatures in the format. Cards which deeply hamper our gameplan, like Collector Ouphe or Grand Abolisher.
An Offer You Can't Refuse: While usually seen as a slightly worse Swan Song, Offer is actually often the stronger choice in this deck. It can hit artifacts, and the swan left by Swan Song turns off Malcolm for that opponent.
Chaos Warp: While steep in its cost, Chaos Warp hits everything. It deals with Planeswalkers such as Karn, the Great Creator and enchantments like Stony Silence, which this deck otherwise can't remove.
Counterspell: The counter by which all other counters be judged. No drawbacks, fancy effects, or restrictions.
Cyclonic Rift: According to Dicebreaker.com, its the third best card in the format. They also put Cultivate at #2, which is ridiculous. So according to me, its actually the second best card in the format. They also put Sol Ring at #1, which surprised me given its obscurity.
Fierce Guardianship: We love spells that get more powerful when our commander is out. This spell will almost always be a free cast.
Force of Negation: While its often a very powerful spell, it has a couple of notable downsides to keep in mind. Like many combat focused decks, opponents will often wait until your combat step to use removal (rather than at the end of the preceding player's end step). FoN doesn't help us there. Additionally, most of our combos are sorcery-speed, where FoN has to be hard-cast. Still, a powerful option in this deck.
Force of Will: Free countermagic helps us at every stage of the game. FoW lets us play aggressively in the early game or combo out a turn or two faster. Don't be afraid to hard cast this, since you may find yourself in a situation where you have lots of mana and few cards in hand.
Mana Drain: How do you like strictly better counterspell? Treat this like any other counterspell, saving it for game-ending threats and big disruptions to our game plan. We have a difficult time utilizing large amounts of colorless mana, and it isn't worth losing protection in order to siphon mana off of somebody's Colossal Dreadmaw.
Mass Mutiny: Mmmmmmm, flavor. Make sure you get the pirate version of this card. Stealing the best creature from each opponents' board can often win us the game.
Narset's Reversal: The "counterspell" with the highest ceiling and lowest floor. This card lacks versatility, since it fails to counter permanents, and only stalls instants and sorceries. However, it also lets us "steal" some really strong cards and access effects outside of our slice of the color pie. This would be the first thing to cut if you wanted to reduce interaction in the deck.
Pact of Negation: While this deck has a really easy time paying for this, we most often use it to protect or disrupt a game-ending combo. Its really bad at protecting our commander early on for obvious reasons.
Sigil of Sleep: Secretly the best creature removal in the deck. Slapping this on Malcolm wrecks most creature-based decks, especially those which rely on creatures staying on the field. Beware of powerful ETB effects.
Siren Stormtamer: Any player who knows what Malcolm does will prioritize removing him as quickly as possible. Stormtamer gives you an easy way to protect your commanders, while also acting as an evasive pirate while on the field. Having a transparent counterspell works really well with inexperienced players as well, since they tend not to play into countermagic.
Spell Swindle: While its initial casting cost is very high, its effect is very powerful. We can also use treasure mana to cast this without too much guilt, since it handily replenishes our stores. While we don't want to use Mana Drain on high CMC spells just for the mana, I will use this to steal oodles of treasure.
Swan Song: Dirt cheap, versatile counterspell with one huge downside. While most decks don't care about giving somebody a 2/2 flier, this deck needs open opponents for Malcolm to connect with. Keep that in mind when you play this.
Vandalblast: Early game, this clears out Sol Ring and Mana Crypt, while late game it works as a total wipe.
Warkite Marauder: Evasive 2-drop pirate with a peculiar little ability. This most often is used for clearing a path for Malcolm, removing flying blockers or other troublesome cards. It can also be used in conjunction with Abrade to kill bigger threats, or used politically to team-up on a particularly annoying creature.
Possible Inclusions
Pongify and friends: Because we have an abundance of mana, we can afford to have more expensive, more versatile removal. Add stuff like this in if your opponents are putting out threats faster than you can get set up.