Consider 2 fort, 1 island, 1 fetch over 4 seachromes

TRON

In

2 Stony Silence
2 Disdainful Stroke
2 Ashiok, Dream Render
1 Force of Negation

Out

2 Path to Exile
2 On Thin Ice
3 Spell Snare

Stony Silence and Ashiok aren't ideal here, but they are better than spot removal. Your game plan revolves around Field of Ruin and counterspells while trying to connect with Sword of Feast and Famine.

BURN

In

4 Leyline of Sanctity
1 Timely Reinforcements
1 Force of Negation

Out

2 Jace, the Mind Sculptor
3 Teferi, Time Raveler
1 Field of Ruin

Mulligan aggressively for interaction here. You don't care about card advantage so much as finding cards that are actually relevant in the matchup. If you don't have a way to deal with an early creature or a Leyline to blank most of their deck, you should probably mulligan.

WHIRZA

In

2 Stony Silence
2 Ashiok, Dream Render
1 Force of Negation
1 Teferi, Time Raveler
1 Cataclysmic Gearhulk

Out

2 Path to Exile
2 On Thin Ice
2 Stoneforge Mystic
1 Sword of Feast and Famine

Cataclysmic Gearhulk is here for this matchup. At times, it's stronger than Stony Silence and is also solid against the creature decks, so it seems like a fine hedge.

Shaving half the Stoneforge package might be a mistake because we're not doing a whole lot with our early mana anyway, but Sword of Feast and Famine rarely connects and there weren't enough matchups where I wanted to devote a sideboard slot to Sword of Fire and Ice.

HUMANS

In

1 Timely Reinforcements
1 Cataclysmic Gearhulk
1 Celestial Purge

Out

2 Force of Negation
1 Mana Leak

This matchup, like Dredge, isn't one that I'm fully prepared for, but it's not a large part of the metagame at the moment.

JUND

In

4 Leyline of Sanctity
1 Celestial Purge

Out

2 Force of Negation
2 Mana Leak
1 Teferi, Time Raveler

Before Leyline of the Void, my plan was to board in the extra Force of Negation and play a tempo game. Now, I think we can play a control game if we want. Leyline can still be used as a tempo tool by allowing you stick to a Stoneforge Mystic and dodge Thoughtseize and Liliana of the Veil though.

AZORIUS

In

1 Force of Negation
1 Teferi, Time Raveler
2 Ashiok, Dream Render

Out

2 On Thin Ice
2 Path to Exile

Teferi, Time Raveler is by far the best card in pseudo-mirrors and is the main reason why I have the fourth copy in the sideboard. Everything in the matchup revolves around it and the rest is just details.

DEATH'S SHADOW

In

3 Leyline of Sanctity
1 Celestial Purge
1 Teferi, Time Raveler

Out

2 Force of Negation
3 Spell Snare

VALAKUT

In

2 Disdainful Stroke
1 Force of Negation
2 Ashiok, Dream Render
4 Leyline of Sanctity

Out

4 Path to Exile
2 On Thin Ice
3 Teferi, Time Raveler

Part of the Leyline / Ashiok plan involves killing Primeval Titan most of the time, so maybe some Path to Exiles have to stay in.

Spell Snare is great against Sakura-Tribe Elder and Explore, but maybe you want to shave one. I could also see only having two Force of Negations, but Scapeshift gets past your other countermagic if you don't have a lock piece in play already.

DREDGE

In

2 Ashiok, Dream Render
1 Force of Negation

Out

2 On Thin Ice
1 Path to Exile

BANT

In

1 Cataclysmic Gearhulk
1 Teferi, Time Raveler

Out

2 Force of Negation

Maybe Ashiok is supposed to come in here. Most of our maindeck cards seem stronger though, so it really depends on what their deck is trying to do. If they have Knight of the Reliquary and Ranger-Captain of Eos, I think I like it, especially on the play.

5C NIV

In

2 Disdainful Stroke
2 Ashiok, Dream Render
1 Force of Negation
1 Celestial Purge

Out

4 Path to Exile
2 On Thin Ice

AMULET

In

1 Force of Negation
2 Ashiok, Dream Render
2 Disdainful Stroke

Out

1 Teferi, Timer Raveler
1 Restoration Angel
3 Spell Snare