Precon Upgrade Guide
Symbiotic Swarm Upgrade Guide
What to cut, what to add, and how to play the Abzan keyword-counters precon from Commander 2020, commanded by Kathril, Aspect Warper.
Commander 2020
Symbiotic Swarm
Counters assembled from the graveyard, with several moving parts. Out of the box, before any upgrades. How we rate precons
Buy Symbiotic Swarm on TCGplayer →Quick verdict
Symbiotic Swarm asks you to stock your graveyard with creatures that have keywords, then cast Kathril, Aspect Warper to turn each of those keywords into a counter on a creature you control. A good Kathril trigger can make one creature, or Kathril itself, a huge threat with flying, lifelink, indestructible and more. It is a slow deck that needs setup, and the box spends too many slots on goad auras and filler creatures instead of milling, ramping, or getting another Kathril trigger.
TurnZero HQ rates Symbiotic Swarm a 4 out of 5 on difficulty and a 3 out of 5 on power, as it comes in the box. That is our editorial read, not an official Wizards rating. The full hundred cards are on the Symbiotic Swarm decklist page, and every other precon we cover is on the precon directory.
How the precon plays
Kathril, Aspect Warper does all its work when it enters. It checks your graveyard for creature cards with flying, first strike, double strike, deathtouch, hexproof, indestructible, lifelink, menace, reach, trample and vigilance. For each keyword it finds, you put that keyword as a counter on any creature you control. Kathril then gets a +1/+1 counter for every keyword counter it handed out, so a graveyard with all eleven keywords puts eleven +1/+1 counters on it in one trigger.
The first job is filling the graveyard. Satyr Wayfinder , Grisly Salvage , Splinterfright and Nyx Weaver mill cards, while Titanoth Rex and Void Beckoner can be cycled into the graveyard and give out a counter on the way. Big keyword creatures like Akroma, Angel of Wrath and Zetalpa, Primal Dawn are as useful in the graveyard as on the battlefield.
The second job is getting more out of the counters. Odric, Lunarch Marshal shares keywords across your board at each combat, so one flying counter can give every creature flying, and Majestic Myriarch picks up every keyword your other creatures have. Netherborn Altar puts Kathril back in your hand from the command zone so you can cast it again for a second trigger.
What works out of the box
Kathril, Aspect Warper ↗
Turns a graveyard of keyword creatures into counters on your board and grows itself for each one. One good trigger makes a hard-to-answer threat.
Odric, Lunarch Marshal ↗
At each combat, every creature you control gains each keyword any of them has. Kathril's counters on one creature end up on the whole team.
Selective Adaptation ↗
Digs seven cards deep for one card with each keyword, puts one onto the battlefield and the rest into your hand, and bins the leftovers. It fills the graveyard and your hand at once.
Satyr Wayfinder ↗
A two-mana creature that mills up to four cards and finds a land. It is the cheapest way to stock the graveyard before Kathril comes down.
Netherborn Altar ↗
Puts Kathril into your hand from the command zone, so you can recast it for another full set of counters. The life loss grows each use, so pick the moment.
Abzan Charm ↗
Exiles a big creature, draws two cards, or adds two +1/+1 counters, all at instant speed for three mana in the deck's colors.
What needs improvement
The deck is slow to get going. Kathril needs a stocked graveyard to be worth five mana, and the box has only a handful of cheap mill cards. Many of its creatures cost five or more, and over a dozen lands enter tapped, so the early turns often go by without much happening.
The goad auras, Martial Impetus , Parasitic Impetus and Predatory Impetus , take three slots and have nothing to do with keywords or the graveyard. The deck also has only one Kathril trigger per cast. Ways to make Kathril enter again are worth more here than most extra creatures, since each new trigger hands out a whole set of counters.
Upgrade ideas
Each upgrade below starts from something the deck does poorly and says what a replacement card has to do. The cards named are examples, not the only answer: if you own something else that does the same job, or a newer printing does it better, it goes in the same slot. Make one change at a time and play a few games between them, so you can tell which change helped. The general method is in how to upgrade a Commander precon →
1. Fill the graveyard sooner
Kathril is only as good as the graveyard behind it. Cheap mill effects in the first three turns mean the first Kathril trigger already has several keywords to find.
What to look for One- or two-mana cards that mill three or more cards, ideally with a creature or land coming back to your hand so you don't lose card economy.
Cut, for example
Martial Impetus A goad aura that makes an opponent's creature attack someone else. It does nothing for keyword counters or the graveyard.
Parasitic Impetus Another goad aura. Draining 2 life per attack is minor, and the slot is better spent on setup.
Predatory Impetus Five mana to goad one creature. It is the most expensive of the three and the least connected to the plan.
Add, for example
Stitcher's Supplier ↗
One mana, mills three when it enters and three more when it dies. A turn-one play that stocks the graveyard twice.
Grapple with the Past ↗
Mills three cards at instant speed and returns a creature or land card to your hand. It sets up Kathril and keeps your land drops going.
Mulch ↗
Reveals four cards, puts the lands in your hand and the rest in your graveyard. It finds lands and mills spells at the same time.
2. Make Kathril enter again
Every time Kathril enters, it hands out a full set of keyword counters again, and the earlier counters stay on your creatures. Cheap blink effects are the most direct way to multiply the commander's value.
What to look for Cheap instants or creatures that exile one of your creatures and return it right away. Anything that resets an enters-the-battlefield trigger works.
Cut, for example
Cartographer's Hawk A 2/1 flier whose bonus only works against a player with more lands than you. Small and unreliable.
Daring Fiendbonder A 5/1 that must attack each combat. It dies to almost any blocker, and its graveyard ability is a single counter.
Add, for example
Ephemerate ↗
One mana to blink a creature you control, then it rebounds to do it again next upkeep. Two extra Kathril triggers from one card.
Cloudshift ↗
One mana to blink a creature you control at instant speed. It also saves Kathril from a removal spell.
Restoration Angel ↗
A 3/4 flier with flash that blinks one of your non-Angel creatures when it enters. Kathril is not an Angel, so it gets a fresh trigger.
3. Ramp toward the top of the curve
The deck is full of five- to eight-mana creatures, and Kathril itself costs five. Two-mana ramp gets the commander out a turn sooner and leaves mana free for mill spells.
What to look for Two-mana spells that put a land onto the battlefield, preferably untapped. Typed land searches can find a land that makes two colors if you add some.
Cut, for example
Cataclysmic Gearhulk Makes every player keep one permanent of each type and sacrifice the rest. A creature deck like this one usually loses more than its opponents.
Sungrass Prairie Needs another mana to produce two colors, so it can't make colored mana alone on the turn you play it.
Add, for example
Nature's Lore ↗
Two mana to put a Forest onto the battlefield untapped, so you can use it the same turn.
Three Visits ↗
Another two-mana untapped Forest. With Nature's Lore it gives the deck two cheap ramp spells.
Farseek ↗
Puts a Plains or Swamp card onto the battlefield tapped, which helps fix the black and white half of the mana.
4. Protect the board once it is built
Once Kathril has spread counters, a single board wipe throws away the whole investment. The deck has Obscuring Haze against combat damage but nothing against a wrath.
What to look for Instants that give your creatures indestructible or hexproof for a turn, at three mana or less or free with a commander out.
Cut, for example
Unbreakable Bond Five mana to reanimate one creature. Unburial Rites does the same and can be cast twice.
Add, for example
Win conditions
The deck wins with one or two huge creatures loaded with keyword counters. Fill the graveyard early, cast Kathril, Aspect Warper onto a board that can carry the counters, and let Odric, Lunarch Marshal spread flying, double strike and lifelink across the team. Blinking Kathril with Ephemerate or Restoration Angel stacks a second set of counters, and the protection spells keep the board alive long enough to swing.
Who should buy this precon
Best for an experienced player who enjoys setup and doesn't mind a slow start. You have to read your graveyard every turn, decide which keywords go where when Kathril enters, and time recasts around the life cost of Netherborn Altar . A player who wants a straightforward creature deck will find it fiddly, and it isn't a good first deck.
Checked against the printed decklist on October 10, 2026.
Track how the upgrades actually perform.
TurnZero HQ keeps a win rate per deck version, so you can change a few cards, play some games, and see the difference instead of guessing.
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