Breed Lethality precon upgrade guide

Atraxa proliferates once a turn, at your end step, and only two other cards in the box proliferate at all.

Atraxa, Praetors' Voice gives another counter of each kind to every permanent and player you choose that already has one, at the beginning of your end step. That's after combat, so the extra counters can't help the attack you just made. The rest of the box leans on that one trigger anyway. Twenty-eight cards name +1/+1 counters (one of them is a land), and the only other proliferate effects are Thrummingbird, which has to connect with a player, and Tezzeret's Gambit, which is a single cast. Four additions change that. Evolution Sage proliferates on every land that enters, Flux Channeler on every noncreature spell, Inexorable Tide on every spell and Contagion Clasp whenever you pay four. Tekuthal, Inquiry Dominus makes each of them, Atraxa included, proliferate twice.

The counters themselves get a second look. The box has two cards that raise how many counters land, Hardened Scales and Corpsejack Menace. Branching Evolution and Winding Constrictor make four. You choose the order replacement effects apply in, so the additive ones go first, and one +1/+1 counter becomes two with Hardened Scales, three with Winding Constrictor, six with Branching Evolution and twelve with Corpsejack Menace.

Two smaller findings sit next to those. The box answers a single creature with Mortify and Putrefy, and it has four sweeper spells (Languish, Merciless Eviction, Sublime Exhalation and Duneblast) for a deck with 28 creatures. And Languish gives every creature -4/-4 while Atraxa is a 4/4.

What are the best Breed Lethality upgrades?

Ranked by how much each does for this deck. Prices are October 2026 market prices at the cheapest released printing, so a few are promo or special-edition copies.

1. Tekuthal, Inquiry Dominus ($1.60). A four-mana flier that reads "if you would proliferate, proliferate twice instead." Atraxa's end-step trigger, Thrummingbird, Tezzeret's Gambit and the four new sources all become two proliferates each. It costs {2}{U}{U}, and the colour table puts that at 72.8% by turn four on 23 blue sources.
2. Evolution Sage ($2.29). A three-mana Elf Druid that proliferates whenever a land enters under your control. With 39 lands in the deck it has plenty to trigger on, and playing the land before you attack puts the counter on before the swing.
3. Flux Channeler ($2.51). Proliferate whenever you cast a noncreature spell. Thirty of the deck's 61 nonland cards are noncreature spells, rocks included, and the trigger resolves before the spell does, even if the spell is countered.
4. Inexorable Tide ($1.06). Five mana, {3}{U}{U}, and it proliferates on every spell you cast, creatures too. With Channeler and Tekuthal out, one noncreature spell is four proliferates.
5. Branching Evolution ($6.78). A three-mana doubler, and the largest single line in the total, argued in the stacking section.
6. Winding Constrictor ($0.46). {B}{G} for a creature that adds one more of each kind of counter that lands on your creatures and artifacts. It's the cheapest way to make the other doublers bigger.
7. Swords to Plowshares ($0.88) and Assassin's Trophy ($1.01). The first exiles a creature for {W}, the second destroys any permanent an opponent controls for {B}{G}. Both are instants, so casting one on an opponent's turn is a Channeler or Tide trigger before combat damage. Trophy lets its target's controller fetch a basic land, which is the price of hitting any permanent.
8. Contagion Clasp ($0.36). Two mana for a -1/-1 counter on a creature, then {4}, {T}: proliferate. It kills an X/1 on the way in and is the sixth proliferate source besides Atraxa.
9. Arcane Signet ($0.38). It makes mana of any colour in Atraxa's identity, so it makes all four, for two mana. The box already has Commander's Sphere and Darksteel Ingot doing that, and a third is cheap insurance for a four-colour deck.

Proliferate before combat, not after

Atraxa's own trigger comes too late to help an attack. Counters put on at your end step are on the creature when the opponents swing back, and they're there when you untap, but the turn you made them was over. The new sources can all fire before combat. Evolution Sage fires on a land drop, Flux Channeler and Inexorable Tide on a spell, and Contagion Clasp whenever you have four mana spare. A land drop with Evolution Sage out grows the board before the swing, and Swords cast during an opponent's turn grows the board before they attack.

Contagion Clasp is the one that needs care. Its enter ability is mandatory, so if you control the only creature in play it has to target yours, and a -1/-1 counter on a creature with a +1/+1 counter cancels it in pairs. Aim it at an opponent's X/1. Every later proliferate can then add a second -1/-1 counter to that creature while skipping your own, since you pick which permanents get the counter.

One counter becomes twelve

Hardened Scales says "that many plus one" and Winding Constrictor says the same for every kind of counter. Branching Evolution and Corpsejack Menace each say "twice that many." Apply the two additive effects first and the two doublers second: 1 becomes 2, then 3, then 6, then 12. Apply them in the other order and a single counter ends at 6. The rulings are explicit that you choose, no matter who controls the sources, so the order is yours at the table. Deepglow Skate and Kalonian Hydra double the counters already on a permanent, and their rulings confirm the same replacement effects apply to the counters those abilities add.

One card in the box can turn that on you. Necroplasm puts a counter on itself each upkeep, and at your end step it destroys every creature whose mana value equals the number of +1/+1 counters on it, yours included. With Hardened Scales out its first upkeep counter is worth two, so it destroys mana value 2 at your first end step and mana value 4 a turn later, where the printed card reads 1 and then 2. The deck has 12 cards that cost two. Proliferate is a choice, so leave it out of Atraxa's trigger. The replacement effects aren't a choice.

Ten cuts, starting with a card the box can't use

Grip of Phyresis gains control of a target Equipment, and the box contains no Equipment. It's live only when an opponent plays one, which makes it the first card out. Festercreep enters with a counter and can spend it to give every other creature -1/-1 for {1}{B}. In a deck with 28 creatures that's a sweeper pointed at your own board.

Cauldron of Souls costs five and gives persist to any number of creatures. A persist creature comes back as a new object with a -1/-1 counter and none of the counters it had, which is the one thing this deck spends its whole game building. Inspiring Call already protects creatures that carry counters, and it stays.

Mirrorweave and Spitting Image are both copy effects. Mirrorweave turns every other creature, yours and theirs, into a copy of one nonlegendary creature until end of turn. The counters stay, but the abilities on your payoff creatures are gone for the turn, and the deck's plan runs on those abilities. Spitting Image is six mana for a token copy of a creature, with retrace. A token copies the printed card and not the counters on it, so it can't clone something you've spent five turns growing. Kalonian Hydra is the exception, since it enters with four counters on its own text, and I'd rather have the Hydra.

Brave the Sands gives your creatures vigilance and an extra block, and Atraxa already has vigilance. Duelist's Heritage gives double strike to one attacker per combat. Sylvan Reclamation exiles two artifacts or enchantments for five mana, and Mortify, Putrefy and Assassin's Trophy cover the same targets one at a time for three mana or less each. It and Ancient Excavation are both landcyclers, which matters little in a deck with 39 lands. Excavation draws cards equal to your hand size and then discards that many, so it filters and doesn't gain a card.

Sublime Exhalation is the cut I'd call closest. Undaunted makes it {3}{W} in a four-player pod, which is a cheap wrath. But the box has four sweeper spells and Bane of the Living besides, and of the four only Duneblast lets you choose a creature to keep. Merciless Eviction at least has three other modes to fall back on. Sublime Exhalation has one.

Where the five-drops stay

Eighteen cards cost five or more in the box. These cuts take four of them out and Inexorable Tide adds one, so 15 remain, and the average mana value goes from 3.70 to 3.47. Seven cards draw the usual objection, too expensive or too narrow, and I think all seven stay.

Ghave, Guru of Spores enters with five counters and spends them one at a time, {1} each, on 1/1 Saprolings. Atraxa's proliferate refills it as long as one counter is left. Elite Scaleguard taps a creature the defending player controls for each attacker that carries a +1/+1 counter. Juniper Order Ranger puts a counter on each creature that enters and one on itself, Cathars' Crusade puts one on every creature you control, and the multipliers make both bigger than they read. Citadel Siege in Khans mode puts two counters on a creature of yours at every beginning of combat. Deepglow Skate doubles the counters on any number of permanents, and the multipliers apply to what it adds.

Duneblast costs seven, {4}{W}{B}{G}, and it's the only sweeper spell in the box that hits every other creature and lets you keep Atraxa. That's the whole argument for it, and it's enough.

The mana, and the lands I left alone

The swaps move the colour sources by one apiece, from 25 black, 25 green, 22 blue and 22 white to 26, 26, 23 and 23. All of that is Arcane Signet. The land count stays at 39, which is higher than the usual 35 to 38, but blue and white still sit one under the table's target (24 for a one-pip spell by turn two, 90% on the play) and black and green only two over it, so there isn't a land I can take out without lowering a colour that has little room to spare. Two-pip spells are still the soft spot. Inexorable Tide and Tekuthal want {U}{U} and the table puts that at 72.8% by turn four on 23 sources, up from 70.2% on the box's 22. Cathars' Crusade and Citadel Siege want {W}{W} at the same 72.8%.

Six lands enter tapped, and the three-colour ones (Arcane Sanctum, Opulent Palace, Sandsteppe Citadel, Seaside Citadel) each carry three of the four colours, which is what a four-colour deck needs from them. The two bouncelands, Azorius Chancery and Golgari Rot Farm, tap for two mana and give Evolution Sage a second landfall when you replay the land they return. I'd leave all six.

Three cards I held back, and a gap I left open

Doubling Season ($30.00) is the first card I'd add. It isn't a Game Changer and it doubles counters and tokens, but it costs more than the ten swaps together ($17.33), and this list already has Corpsejack Menace and Branching Evolution doubling counters. Contagion Engine ($13.13) proliferates twice for {4}, {T}, and its enter ability puts a -1/-1 counter on each creature a target player controls. It costs six to cast and {4} per use, where Contagion Clasp costs two and {4} for one proliferate, and Tekuthal doubles either. Karn's Bastion ($2.71) is a proliferate land, and it taps for colourless in a deck that is already short on its two-pip colours.

The mana is the other place money goes. Hallowed Fountain ($7.18) and Watery Grave ($9.90) would be the untapped duals that matter most, and I'd wait on them: Scryfall lists all ten shocklands in Star Trek on 13 November 2026, which may move those prices.

The deck's draw is the gap I left open. By my count it stays at seven draw effects, below the usual 8 to 12, and the best fix is Rhystic Study ($60.11). It is a Game Changer, and one Game Changer lifts the bracket floor to Bracket 3, so it's a choice about your table before it's a choice about money.

The upgraded decklist

Atraxa and the 99 with all ten swaps made, sorted by card type. Hovering any name shows the card.

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FAQ

Does proliferate help my opponents?

Only if you let it. Proliferate lets you choose any number of permanents and players that already have a counter, including none, so Atraxa's trigger can skip an opponent's creature with a +1/+1 counter and still grow your own. It also means you can add another -1/-1 counter to an opponent's creature that already has one and leave your own alone.

How many cards in Breed Lethality proliferate?

Besides Atraxa, two: Thrummingbird and Tezzeret's Gambit. The upgrade adds Evolution Sage, Flux Channeler, Inexorable Tide and Contagion Clasp, which makes six, and Tekuthal, Inquiry Dominus doubles every one of them.

Can Reyhan and Ishai lead this deck instead of Atraxa?

They can lead it as a pair. Reyhan, Last of the Abzan is black and green, Ishai, Ojutai Dragonspeaker is white and blue, and both have partner, so together they cover the same four colours Atraxa does and every other card stays legal. It's a different deck, though. They are a 3-mana 0/0 and a 4-mana 1/1 flier, and the swaps in this guide are written for the commander who proliferates.

Is Contagion Clasp safe next to my own counters?

Mostly. Its enter ability is mandatory and needs a creature target, so aim it at an opponent's X/1. If you have to put the -1/-1 counter on your own creature, it cancels against a +1/+1 counter there as a state-based action. Later, each proliferate can grow that opponent's -1/-1 counter while you leave your own creatures out of it.

What does the whole upgrade cost?

$17.33 for ten cards at the cheapest released printing, as of October 2026. Branching Evolution is $6.78 of that, and the other nine add up to $10.55.

Does Languish kill Atraxa?

Yes, unless she's carrying a counter. Languish gives every creature -4/-4 until end of turn and Atraxa is a 4/4. Duneblast is the sweeper in the box that lets you choose a creature to spare, and it doesn't target, so you can name her.

Is Doubling Season worth buying for this deck?

It's good, and it's the first card I'd buy after this list. It costs $30.00 at the cheapest printing and it would be the third doubler on a list that already has Corpsejack Menace and Branching Evolution. It also doubles the tokens from Migratory Route.