Last time, I broke down the best options for your Affinity sideboard. Today, I’ll cover the matchups, but I’m not going to provide fixed sideboarding guides this time. One reason is that I find myself switching things up all the time depending on who is on the play and the particular card choices of my opponent. Moreover, the Modern format is changing so rapidly right now—with new Eldrazi variants and anti-Eldrazi decks cropping up every day, any fixed guide I give now would likely be out-of-date in a few weeks. Finally, your Affinity version might be different from mine.

So instead, I’ll focus on general sideboard advice. My aim is to teach you to catch a fish.

Generally, you can always board out the following cards:

  • One 0-cost creature: typically Memnite, but boarding out an Ornithopter against a non-interactive combo deck is fine too.
  • One 1-cost creature: Signal Pest is usually the worst one, especially if you play against a deck with flying blockers, but Vault Skirge can be even worse against combo decks like Storm where your own life total doesn’t matter.
  • One or more colored spells: I try to adhere to a maximum of 8 colored spells for post-board games. Especially when you’re bringing in colored spells from the sideboard, I am always willing to shave a Master of Etherium, Thoughtcast, or Ensoul Artifact. Master is worst against removal-heavy decks. Thoughtcast is worst against fast combo decks. Cutting Galvanic Blast is wise if your opponent isn’t trying to assemble creature-based combos.
  • A 17th land when you’re on the draw: Cut an Island against Lord of Atlantis, or if your opponent doesn’t have Path or Ghost Quarter. Cut Glimmervoid if you’re not adding many colored cards, and Blinkmoth Nexus if your opponent is playing a super-fast deck.

So it’s easy to make room for 3 sideboard cards in every matchup. In addition to the above, you can remove the following cards in certain matchups:

  • More Memnite and Signal Pest against slow, attrition-based matchups. These are low-impact threats, so I tend to shave another Memnite against a deck with tons of ground blockers, and I often cut multiple Signal Pests if I’m up against a deck with Inkmoth Nexus, Lingering Souls, or Vault Skirge.
  • 1 Steel Overseer when you’re not in a combat-centric matchup. I always keep 4 Overseers against Affinity or Eldrazi, but I don’t mind shaving one against most other decks, especially when they contain Pyroclasm or Stony Silence.
  • If you have Etched Champion in the main deck, then cut that one against colorless decks or non-interactive combo decks.
  • If you have Spellskite in the main deck, then board it out if the 0/4 isn’t going to block and/or if your opponent isn’t trying to resolve cards like Become Immense or Daybreak Coronet, and/or if your opponent isn’t going to cast Kolaghan’s Command.
  • If you have Welding Jar in the main deck, then cut it if your opponent has fewer than 6 cards you want to regenerate from and/or if they have multiple Spellskite.

Eldrazi Decks – Slightly Favorable

Against the colorless Eldrazi deck, bring in Ancient Grudge and cut an extra Memnite when you’re on the draw, but not when you’re on the play (they likely keep Chalice of the Void when they are on the play for the turn-1 Chalice on 0, but not when they are on the draw.) Don’t board in Whipflare, Torpor Orb, or Thoughtseize.

Against blue Eldrazi variants, which I expect to become more popular than the colorless Eldrazi variant, I would add Whipflare and, if you have it, Torpor Orb. These cards help against Eldrazi Skyspawner and Drowner of Hope. Thoughtseize is good too against Hurkyl’s Recall or Stony Silence.

Against the RG Eldrazi variant, you’ll have to fight through Kozilek’s Return, Lightning Bolt, and Ancient Grudge. Stubborn Denial is fine against those cards, whereas swarm cards like Signal Pest or Steel Overseer can be boarded out more readily.

Spellskite, Dismember, Painter’s Servant, Ensnaring Bridge, and Blood Moon are good against every Eldrazi deck. Etched Champion and Welding Jar are rather weak, so don’t forget to board them out if you have them in your main deck.

Affinity – Even

Add Ancient Grudge, Ghirapur Aether Grid, Dismember, and Spellskite. Sea Gate Wreckage is good if you have it, but Thoughtseize is not. Cut most or all Signal Pest, a colored spell or two, and sometimes an Island. Etched Champion should go if you have it main, but you can keep Welding Jar if you want—it’s embarrassing against Spellskite, but saving a Steel Overseer from a removal spell can decide a game.

Remember that Spellskite can deflect the modular ability of Arcbound Ravager, but opponents can choose not to put counters on the 0/4 when it resolves.

Abzan Company – Slightly Unfavorable

Add Grafdigger’s Cage, Dismember, Whipflare, Thoughtseize, and Ghirapur Aether Grid. Gut Shot is good too if you have it. Don’t bother with Etched Champion because it’s too slow. Welding Jar should be cut if you have it main.

They usually have Kataki and Path to Exile after board. In addition, mind the Chord of Calling for 4 that gets Linvala (sacrifice permanents to Arcbound Ravager before it resolves) and the Chord for 3 that gets Orzhov Pontiff (don’t attack with that Nexus if you don’t have to).

Infect – Unfavorable

Add Spellskite, Ghirapur Aether Grid, Dismember, Thoughtseize, and Whipflare. Chalice of the Void is great if you have it. Cut most or all Signal Pest, a colored spell or two, and sometimes an Island.

Because their kill is typically faster than you, you should mulligan most hands without a piece of interaction. One thing to keep in mind during the games is that Vines of the Vastwood can counter the modular effect of Arcbound Ravager, so don’t go all-in unnecessarily if your opponent has a green mana available. This is even more true when you factor in Nature’s Claim, a popular sideboard card.

Naya Burn – Favorable

Board Etched Champion, Spellskite, and Stubborn Denial. Retain Welding Jar if you have it main. If you have Chalice of the Void and are on the play, then board that in. Since you add 3-drops and they often add Destructive Revelry, Path to Exile, and Deflecting Palm after board, Master of Etherium loses value and you should cut two copies or so. Remember that Deflecting Palm, which doesn’t target, can still redirect the damage from Etched Champion.

Jund Midrange – Slightly Favorable

Add Etched Champion and Stubborn Denial. Spellskite and Sea Gate Wreckage are good too if you have them. Same goes for a possible main-deck Welding Jar. Cut Galvanic Blast, Master of Etherium, and a Memnite. When you’re on the draw, an Island can go as well.

Merfolk – Favorable

Add Dismember and Thoughtseize. Whipflare is mediocre but playable. Besides the usual Memnite, always cut an Island, even when you’re on the play, because it just turns on their Lord of Atlantis. You can cut an Arcbound Ravager too because it’s poor against Hurkyl’s Recall and Vapor Snag.

I could go on, but by now you should have the tools to figure out how to board in any other matchup with your specific list of Affinity. Hope this guide was useful to you, and may the following 8 cards always smile at you after your first draw step: