Everything You Need To Know About Parasitic Cards in Magic

Steve Vrooman February 14, 2024 Collecting, MTG Cards, MTG Rules

Last updated on March 22, 2024

Desperate Ritual | art by Wayne Reynolds

When I think of parasites I think of heartworms, face-huggers, paparazzi. But the MTG community has a different concept of parasites: mechanics and cards. It uses these concepts discuss how card designs and mechanics interact with the rest of the card universe.

And everyone seems to have a different understanding of what that means! With a muddled topic like this one, it’s important to consider all the available information to find clarity among the opinions. Thankfully, MTG designer Mark Rosewater has given us plenty of thoughts about parasitic mechanics to work with.

Let's try to sort all this out!

What Are Parasitic Cards?

Boromir, Warden of the Tower | Illustration by Yigit Koroglu

Parasitic cards and mechanics are reliant on cards from their release set to function properly. But design concepts are often more complicated than a few words suggest, which is why there is a lot of misunderstanding and debate.

A parasitic mechanic is, in the words of Mark Rosewater, one that “only works with a subset of cards from the set/block it’s in. For example, splice onto arcane only worked with arcane and that only existed in Kamigawa block.” But Rosewater also notes that “parasitism is a scale, so mechanics aren't necessarily parasitic or not, there are degrees.” What are these degrees? Rosewater is less clear there, further complicating the topic. The discussion of mechanics also muddles how individually parasitic cards slot into the larger conversation of parasitism in MTG.

How Does Linearity Relate to Parasitism?

When it comes to the question of how specific parasitic cards relate to potentially parasitic mechanics, Rosewater has repeatedly noted that what people are really talking about is linearity. Adventures, for example, isn’t a parasitic mechanic. People can and do play Bonecrusher Giant for fun and profit as the only adventure card in their deck.

But there are cards like Lucky Clover or Astral Slide that reward “linearity,” or putting a lot of one card type or mechanic in your deck. Lord of Atlantis does the same thing. It’s a classic piece of MTG design space, and every mechanic (and almost every card and creature type) has some linear elements and cards. So that is not an indication of parasitism. As Rosewater notes, “Yes, we’ll make cards that encourage you to play a lot of the same mechanic in a deck, and that might even be a tournament-viable strategy. None of that makes a mechanic parasitic though.”

For Rosewater, the most parasitic cards are almost anti-linear. These are mechanic-specific sideboard cards: “Can something be parasitic and not linear? Yes. The best example is sideboard cards created for a specific environment. (Take Melira, Sylvan Outcast from New Phyrexia for example) These cards have no place outside the environment they were created in, but they’re not linear in that they don’t push you to add specific cards to your deck.”

But let’s back up. Why are cycling and adventures not parasitic, even though they can be built into very linear decks that feel very insular and on rails? This is where it gets complicated. It goes back to the question of support, which is how questions of parasitism changes over time, and the question of playability, which is how Rosewater talks about a scale of parasitism. Let’s tackle support first.

How Does Design Support Affect Parasitism?

Battles are the newest card type in MTG. We can imagine a future in which various kinds of linear support are added to the game to synergize with battles. Perhaps something like “affinity for battles” makes a card cheaper. Perhaps an aura that can enchant battles. Those auras and affinity cards would at first seem parasitic because there aren’t enough cards in the game for them to support; you would need to play a very small handful of cards from a single set to make them function. But if the game advances to a place where battles were printed with the frequency of auras or sagas, it would make synergy pieces, like “affinity with battles,” seem less parasitic because they would work with a larger portion of Magic’s card pool.

Part of the reason Rosewater talks about a sliding scale of parasitism is that there is very little inherent in a card design that makes it parasitic. Parasitism is defined by a card’s playability outside it original release environment, and that environment can become more friendly to a mechanic or card type over time.

For example, in 2011, Rosewater considered samurai to be parasitic because the card type and support pieces were only in Kamigawa block. But now that more samurai were printed in Kamigawa: Neon Dynasty and March of the Machine, plus some one-offs in other sets, the mechanic’s degree of parasitism has changed. Samurai might still be parasitic, but they are less so because they have stronger support.

In arguing that Eldrazi colorless mana casting costs were not parasitic, Rosewater relied on strong design support over time for colorless mana: “Parasitic means it is making use of a resource found only in the set it is in. Colorless mana has been in the game from the start and there are lots and lots of ways to produce it over the last 22 years.” He makes a similar argument for the party mechanic: “Party – not remotely parasitic; Magic has 27 years of making Clerics, Rogues, Warriors and Wizards.”

That brings us to the last, most complicated question:

How Does Playability Relate to Parasitism?

In 2013 Rosewater said, “Things like horsemanship take something very natural to the game and make it parasitic (meaning that it only interacts with other things in the set rather than the rest of Magic).” So horsemanship is like a parasitic take on flying (designed for the world of Portal: Three Kingdoms, where things didn’t fly).

But before, and especially after that, Rosewater has used playability as the answer to questions of parasitism pretty repeatedly. For example, his analysis of lesson/learn: “Lessons – a little parasitic in there’s logistics in preparing for the first one which further cards can benefit from; again, you can play one and get full mechanical utility, so just a tiny bit parasitic.”

And by 2023, they reprinted Sun Quan, Lord of Wu into Commander Masters precisely because horsemanship is really good. Shadow and horsemanship could be interacted with heavily in their original environments, as creatures with those abilities were more common, allowing players to block these evasive creatures regularly. But now horsemanship and shadow basically mean “unblockable,” which is much stronger than either ability. I doubt Rosewater’s take on horsemanship would be the same today given how he’s answered recent questions about parasitic mechanics.

This still leaves us with another question about playability, and that comes down to individual card design versus overall mechanical design and support. Cards can be made to stand on their own or require their fellow cards from their original context. Rosewater’s analysis of energy helps us here: “Energy is definitely parasitic. I’ve been pointing out that we executed it in a way to make it less parasitic.”

This execution is with cards like Aethersphere Harvester. It produces its own energy, making it an independently functional card. If you have no other energy cards, you can still give it lifelink twice, but the vehicle really pops off in an energy-rich format.

If we take Rosewater’s palatability axiom to heart, “Adventures – not remotely parasitic, you can easily play one in deck with full utility,” it seems clear enough, but it isn’t. You really can’t get full utility out, say, Ardenvale Tactician outside of Limited because although you get the full use of the mechanic, no part of the card is good enough to be good enough for Constructed play, even in very linear Lucky Clover decks.

But the mechanic of adventures, like lesson/learn, is inherently stronger as a mechanic because it is literally a two-for-one on each card. Compare that to oil counters. Like an energy counter or day/night, an oil counter is structurally meaningless. It does nothing on its own. Some cards are good, like Urabrask's Forge because they utilize the mechanic to produce independent value, but many, such as Kuldotha Cackler, are more parasitic because they don’t bring their own value.

Could we say that designs at the lower end of the parasitic spectrum have a high density of independently-playable cards, and that cards higher on the spectrum have fewer cards that are good enough to play alone? That seems to be the direction Rosewater is going: “Dungeons – it’s medium parasitic in that the farther you venture in the dungeons, the stronger the effects get; you can still play just one though and get full mechanical utility.”

Ah, so one more wrinkle! There is a difference between what Rosewater calls “mechanical utility” and what we might call “meta utility.” Adventures interacting with exile means each card is even more than its mechanical on-card two for one because of a recent surge in “cast from exile” support on cards like Pia Nalaar, Consul of Revival, Prosper, Tome-Bound, and The Thirteenth Doctor. That takes us back to the interaction with design support, and how a mechanic’s degree of parasitism can shift over time.

Let’s pull these definitions together with two test cases:

Testing Parasitism: Putting It All Together

Let’s see if we can figure out how to apply Rosewater’s perspective on parasitism to two recent mechanics.

Test Case 1: The Ring Tempts You

The Ring Tempts You has two kinds of effects: those that tempt you and those that reward you for getting tempted. Both are playable. Because many of the cards in both camps are reasonably fine if not good on rate even if you have no other Ring cards in a deck, the mechanic is not parasitic at that level. Think of Aragorn, Company Leader and Boromir, Warden of the Tower. Even a card like Birthday Escape is playable as the only Ring card you have. A one mana cantrip matters, even at sorcery speed. And giving something a version of skulk is fine enough value, even if you never move any farther on the Ring temptation chart. Even if you have no cards that make the ring tempt you, Gandalf, Friend of the Shire is a perfectly functional flash creature that empowers your sorceries.

There are also quite a few Ring-oriented cards that function independently. Frodo Baggins is fine on his own, and I have a few Commander decks where I run The Ring Tempts You as the only card with the mechanic. These independently playable cards demonstrate that the mechanic is not inherently parasitic.

Test Case 2: Dungeons & The Initiative

These mechanics are interesting to discuss together, as most of the dungeons from Dungeons and Dragons: Adventures in the Forgotten Realms were too underpowered to matter outside Limited, while the initiative cards from Dungeons and Dragons: The Battle for Baldur’s Gate were so good they kind of broke Legacy and Pauper.

This mechanic perfectly embodies the difficulty of this discussion. Many people considered these designs parasitic, but they are generally not. The dungeons are more cardboard to keep track of, yes, but venturing into the dungeon is a buff that happens on ETB, on attack or via casting certain spells. That isn’t dissimilar to getting a +1/+1 counter as a bonus of game actions like on Snakeskin Veil and Ironpaw Aspirant.

Perhaps the issue for folks is the number of parasitic cards that are synergy pieces. The more cards that reward you for venturing into the dungeon, like Dungeon Delver or Gloom Stalker, the more parasitic a mechanic tends to feel. Now that we have a firm understanding of what a parasitic card is, let’s look at some of MTG’s most parasitic cards:

Types of Parasitic Cards

#10. Corrupted

This recent mechanic from Phyrexia: All Will Be One is an interesting place to start. It is high on Rosewater’s parastism scale since only seven of the 24 corrupted cards have toxic or create tokens with toxic, so cards like Bonepicker Scourge are unplayable outside of their Limited environment!

But many of these cards are playable on rate if you ignore the corrupted text. Bring the Ending is just Quench with mechanic-specific upside; the same can be said for Distorted Curiosity as a respectable Divination upgrade. Anoint with Affliction is a strictly better Eliminate that sees plenty of Standard play in decks without a poison counter in sight.

This is the Bear with Set's Mechanic joke’s design space. It’s parasitic, sure, but not in a meaningful way and seems a necessary stop on the design train’s tracks.

#9. Recover

Theoretically playable outside their Coldnsnap environment, cards with recover aren’t only overcosted, but the mechanic is quite awkward. When the recover ability is triggered, which is often not your choice, you must pay an exorbitant cost at that precise moment to get the card again or it’s exiled from your graveyard. So, these cards give you full mechanical utility, but they never give you sufficient meta utility:

If these cards were good enough on rate, the design itself isn’t the most parasitic thing in the world.

#8. Eldrazi Using Exiled Cards as a Resource

Turning the exile zone into an accessible zone that can be used as a resource isn’t a named mechanic, but the wording that allows you to take one or more cards “opponents own from exile” or “an opponent owns from exile” and put them into graveyards is on:

The parasitism of this effect has shifted radically. These cards are from Battle for Zendikar, and in that set even draft common removal spells like Complete Disregard exile their targets. There were far fewer cards in exile in normal sets at that time, so these Eldrazi were parasitic because you needed so much interaction from their set to function. But, as exile effects have increased in MTG, these cards become more relevant. You don’t need over costed cards like Brutal Expulsion to enable your cards. They have become less parasitic, but still, you would not likely feel safe just jamming these in decks.

#7. Morph & Megamorph

Do you play any morph cards in Commander outside of the Kadena, Slinking Sorcerer deck? Morph is fantastic in Limited, as the much-beloved Limited format Khans of Tarkir demonstrates, but a mechanic’s strength in Limited does not guarantee meta utility.

Morph is mana inefficient. Even in modern Limited formats, a vanilla 2/2 for 3 is unplayable. Spending more mana to flip the card, even with synergy pieces on board like Secret Plans has rarely been enough to make a Constructed deck, even with about 200 morph cards to choose from. Some decks have benefited from individual morphs, like Den Protector, which is the only reason this mechanic isn’t higher on the list.

With a few exceptions, morph cards are unplayable outside of their original environment, unless you have something like Kadena removing the exact inefficiencies these morph cards bring to the table.

#6. Slivers & Allies & Rebels & Mercenaries

Are these parasitic or are they just really, really linear? How is a card like Cloudshredder Sliver that different than, say Priest of Titania? Neither is really playable outside of their creature typal decks. The trouble is comparing Llanowar Elves to Lin Sivvi, Defiant Hero. One is good in any deck than can cast it, regardless of additional typal synergies. The other is only busted in Constructed formats when its fellow creatures enabled it.

The cards for these four creature types are parasitic and unplayable, mostly, outside of their creature type space. But the delta of how good they can be in those typal spaces is so much higher than for other creature types, although arguably every creature type matters card has a whiff of parasitism to it.

#5. Soulshift

Along with offering from Betrayers of Kamigawa, soulshift is a classic example people use to talk about parasitic designs. If you look at the offering cards, though, they are clearly as playable as any creature type matters cards would be, as long as the creatures exist outside of the plane’s setting, which is trouble for Patron of the Moon but is a solvable problem for Patron of the Kitsune. And a cursory look suggests that soulshift cards are playable; spirits are a fairly well supported creature type, so it should be easy to get full mechanical utility from soulshift cards.

But let’s look further and consider meta utility. Soulshift requires you to play with a curve of stacked mana costs for your spirits so that you can return a chain of them from your graveyard. It also likes self-mill. Outside of that deck design, a card like Crawling Filth costs like four mana too much to play, even in Limited. This parasitism is further amplified by the fact that spirit typal decks tend toward tempo decks with cheap cards like Spectral Sailor and Rattlechains. This dissonance prevents soulshift’s mana curve restraints from being useful.

But that doesn’t have to be the case. There are ways of building out spirits that would let soulshift work. Imagine if you had a mechanic like prototype for spirits that would let you get the big mana cost bodies onto the battlefield more easily. Plus, if more cards had bigger “soulshift n” formulas on cheaper cards, which goes against most of the designs from Kamigawa block, they would be immediately playable. Promised Kannushi, for example, could easily get busted with the right kind of spirit and graveyard design.

So that’s why, even though soulshift seems to be the poster child for parasitism in discussions about the issue, it is lower on the parasitism scale.

#4. Energy

Any new resource will feel parasitic. The excitement folks have over energy’s return in the Fallout precons is what parasitism feels like, especially from an EDH perspective. If I can’t play my energy cards outside of Aetherworks Marvel in a Commander deck because I don’t have enough cards to reach a critical mass of my mechanic, there’s a chance that’s parasitism in action! And because energy was so broken in its Standard, WOTC seems a bit slow to take it up again, even though we’ve had many sets the past two years you could see it working in thematically. So, the delta between the power of the cards in a parasitic space and in one that isn’t is large.

#3. Splice onto Arcane

Arcane was a spell subtype introduced in the original Kamigawa block. Many of those cards had the splice onto arcane mechanic in their text. This is a complicated ability, but it allows you to add a card’s effect to another arcane spell you’ve cast by revealing it from your hand and keeping it in your hand. So, like a parasitic form of buyback? This is kind of a hallmark of the traditional idea of parasitism, but many of these spells are competitively costed, including great cards like Goryo's Vengeance and Through the Breach that see play with no other arcane cards.

Splice has been in recovery mode since Modern Horizons, which decoupled it from arcane and gave us “splice onto instant or sorcery” with Everdream and Splicer's Skill. Not parasitic. Not particularly good.

#2. Bursts

This mechanic doesn’t have a coherent name, so I’ve named it after the first cycle of such cards, the burst cards from Odyssey:

But it all started with Tempest’s Kindle. Each card buffs its result of casting based on the number of cards with the same name in your graveyard. There are some synergy pieces to the burst cycle proper, with Diligent Farmhand and Pardic Wildcat.

This is a design space WOTC has returned to, and of course these are pretty much unplayable in Commander, which reveals the strong form parasitism inherent in these cards. The others, some of which I’m sure you've played, are:

Some look at all graveyards. Some just yours. Exciting, right?

#1. Ripple

Ripple is similar to burst in that the mechanic only works with a critical mass of cards with the same name, but it manages to be even more parasitic because it has far less synergy with cards outside the cycle Each card uses the “ripple n” formula to check the top cards of your library for a card that shares a name with the ripple card you cast, allowing you to cast addition copies. Each card in the cycle has a mana value about double its general playability, with the red one being the closest to fine:

There is also a kind of ripple lord card, Thrumming Stone, which has been reprinted in Double Masters and has been on The List. That card works well in Dragon's Approach and Rat Colony decks that provide more hits.

Because the colored set of ripple cards work only with themselves, this is about as insular as you can get. They don’t work at all in singleton formats like Commander, and their overcostedness make them useless for constructed.

Are Parasitic Cards Good for Magic Design?

Most Magic cards are parasitic from a certain lens. Auras, equipment, and any spell that targets creatures require, well, creatures. If you’ve ever held a grip of removal against a superfriends deck, you know what I mean. Cantrips require you to have a deck! An Offer You Can't Refuse and Blood Moon and Bojuka Bog are answers to specific opponents but not others.

Parasitism is just an expansion problem. A game with limits, like Monopoly, has parasitic pieces, but they are the flavor (“Get Out of Jail Free” cards) and the endgame (hotels), and there are no other expansions of the game to compare them to. Games with limited expansions, like Settlers of Catan, have some content that feels parasitic, like a strange subgame, say, the Trader and Barbarians expansion. Because Magic has such a large number of expansions, it’s not possible for every card to interact with every other card.

WOTC design works with this over time, returning to successful mechanics and expanding their design space to interact with more and more cards. Think about potentially parasitic spaces like those occupied by madness and how many other elements of the game they connect with.

Without some parasitism, Magic design would stagnate. Everything would ever only be kicker or something like prowess that interacts with most things. At the same time, big picture, you wouldn’t want every card to be playable only in its Limited environment, especially in a time when EDH is the most played format in the game, and one of its biggest appeals is the ability to play cards from every Magic set.

The cleanest answer to this question is likely one we won’t like very much. In an era of reasonably constant power creep, parasitic design doesn't matter a whole lot. If I make a Hill Giant as a one drop, it doesn’t matter if the set mechanic, “speldifery,” only works with other splendiferous cards. It’s still a 1-mana 3/3. And if that’s the MTG world we are living in, some form of parasitic design is actually necessary to slow down the power creep roll!

Wrap Up

Feast of Flesh | Illustration by Volkan Baga

We love playing “x decks” – elf typal, artifacts matter, gates, superfriends, scry matters, madness, defenders, whatever. Part of the fun of Magic is deck design, and we like to find linear synergies and exploit them if we can. And sure, we love to get Lost Caverns of Ixalan’s new merfolk support to fill out the pieces of our merfolk decks, but we don’t necessarily like to just jam the new powerful cards or decks without putting our stamp on them. Even a superpowered Commander precon, well, we want to tinker with it just a bit.

For many of us, our favorite thing is when a new card’s design triggers some great combo with an older card we might have forgotten about, like when folks figured out that when they put Retreat to Coralhelm into their Galadriel of Lothlórien decks as a synergy piece, it actually makes a busted combo with the long forgotten Scouting Trek. This is also the pleasure of Eternal formats like Pioneer and Modern. And it also has to be a design pleasure for WOTC, making Greasefang, Okiba Boss knowing Parhelion II was lying in wait, or Amalia Benavides Aguirre when Wildgrowth Walker was chilling.

But that pleasure requires every card to not be awesome in every game state. That joy, and the pleasure of a format with a diverse suite of decks rather than one or two dominate strategies, requires some cards to have limited designs. We need to pay some kind of price for linear power, or WOTC needs to use the ban hammer to balance things.

Designs we call parasitic allow these possibilities by creating delimited streams of synergy. Parasitic design also leans into story and flavor and the pleasures of seeing something new in the way we play the game. Given the vast number of Magic cards and sets (link to my article on this when it’s published), and the large number of mechanics, card types and designs over these thirty years, the fact that we complain about only a handful (maybe two hands full!) of parasitic mechanics feels like success for WOTC design.

What do you think? Have we missed a glaring bit of parasitism? Let us know in the comments or on Discord!

Stay safe, and keep brewing!

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Steve Vrooman

A casual MTG warrior since Ice Age, Steve would have liked to have seen at least one card with cumulative upkeep in Kaldheim. He likes to think he'd be in Lorehold, but it's probably Silverquill.