How does Dredge sideboard in the mirror match?

I'm not going to post decklists, because it's all theoretical. But lets assume both builds play Dread Return and then lets talk about ubiquitious main deck cards:

Basically, I have around 8 cards in my sideboard I would bring in for the matchup, but don't know what cards I would board out.

Does Serum Powder stay in or would do these get boarded out? My Leylines of the Void are in sideboard, and think substituting Leylines 1 for 1 with Powder is a reasonable way to sideboard the matchup.

Cabal Therapy doesn't really get any cards from the opponents hand, but you it does create sacrifice outlets if you have bridge from below online. Basically, it quickens the deck and is an engine.

Dread Return still seems like the best path to victory, if you can remove an opposing leyline of the void. But you could remove Dread retun and all the targets for it, streamlining the deck a little better.

Ichorid still seems very usefull to exile opposing Bridge from Belows.

Are there different sideboarding theories for being on the play vs the draw? Put otherwise, would you have a different sideboard in game 3 than game 2?

Why would you keep LotV in the board? Is that a typo? Also, Serum Powder seems like a no-brainer to stay in the maindeck, but I'm not a Dredge pilot.

@BazaarOfBaghdad They start in the board, so I have to board them in. I could see how my phrasing could be confusing.

What's wrong with sideboarding out Serum Powder? Do you really think you can never side these things out, in any matchup?

If I was playing a Brophy style Dredge deck, against another Brophy style deck I would board in:

• Wispmare; good against Leyline and removes Bridge from Below
• Leyline of the Void; if it's not in your maindeck, but in your side.
• Nature's Claim/Serenity
• If you have it: Chain of Vapor (also gets Elesh Norn)

I would keep in Therapy, since it can get their sideboard cards out of their hands.

I would shave some cards here and there, but not to much. The matchups is about speed. Petrified Field is an obvious side-out.

With a Brophy style Dredge deck against a Pitch Dredge deck, I would only board:

• Leyline of the Void
• Chain of Vapor (against Marit Lage)

With a Pitch Dredge style deck, against a Brophy style deck I would transform, removing all counterspells and shave 3 more cards.

With Pitch Dredgde against another Pitch Dredge deck, I would side out 4 Petrified Field and other cards for
4 Urborg and all Hexmages.
Hexmage can be sacrificed to exile their Bridges, while giving yourself more tokens. And Urborg lets you cast Hexmage, Thugs and Imps.

The whole MU is about Bazaar still and the speed of winning the game, but Leyline changes the dynamic a bit if one or both of you has it in your list. So you don't want to sacrifice your speed. You should leave in your maximum number of dredgers, powders, bazaars, dread returns, ect. and plan to mull to Bazaar. Outside of Leyline the best disruption cards are Karakas (if they are on dragon), and Strip effects.

I put in any enchantment hate I have, and put in at least 1 set of depths/stage if I have them in my deck. I take out any counterspells/unmasks/other cards that have minimal impact on the MU. Then shave down on a therapies, and other non-integral cards to winning the game.

Cabal Therapy is nice, but its really not critical to the MU at all. It removes your opponents bridges, but only at sorcery speed. Ichorid is much of the same. You have to remember that because of this your Bridges will almost never survive passing the turn.

A lot of the side boarding is only relevant if your opponent decides to keep a leyline, and no bazaar hand or if both of you have a leyline. As such not a lot of the cards matter. Serenity is quite awful actually in this MU because its hitting your own leyline as well, and takes until turn 3 before you can even get your first Bazaar activation in. Similarly, you can't rely on a fast depths combo to win the game, even if you get it on turn 2 they can just chump it with Narcomoebas (which I've had happen).

Claim, and Wispmare are really the only good anti-hate cards. Chain of Vapor again is marginal because of its mirrored effect.

@vaughnbros

Is it ever correct, in any matchup, to board out the Serum Powders? Or should you just find some other card that might slow you down, instead of making you less consistant.

@gkraigher Boarding out 1 Serum Powder seems fine as long as the cards you are bringing in are highly relevant.

@gkraigher Not in the mirror. That's the most important card other than Bazaar.

I board them out in every other MU pretty much.

@vaughnbros

You board out serum powders in every other matchup but the mirror??

@gkraigher Against anything other than the mirror and combo, yes. It's a terrible top deck, and I'm not mulliganing that much.

Do not cut powders. You need every rebuy on mulligans you can get because bazaar and sideboard cards are that important in the matchup. I've never cut Bridges/narcs/stinkweed/troll/bazaar/powder. That's the bare minimum the deck needs to function properly

Noard out misstep. Board out therapies, Board out maybe a few lands as most lists need them postboard against shops but you'll only need 1 rainbow to cast wispmare/CoV/Nature's claim. Board out ichorids.

Postboard becomes a race to Elesh norn most games.

@tammit67

Cabal therapy acts as removal for bridge from below, while stripping castable creatures from your opponent's hand. Seems good in the mirror

@gkraigher Castable creatures aren't a thing. Therapy is just a worse wispmare with mana available, as you get tokens and remove theirs and hits leyline. It's not so bad that I cut them first (removing bridges is a big deal for sure) but usually I have enough to bring in that they get cut anyway.

Dredge AT MOST affords either Maindeck or Sideboard Leylines, because the entirety of their Sideboard must answer anti-dredge cards.

That said, if I win game 1 AND don't see leylines, I would be hardpressed to sideboard ANYTHING in game 2.