Tricky Rules Interactions, Explained: Ikoria Edition


Ikoria: Lair of Behemoths must be one of the most complicated sets of all time, although many of the judge calls concern just one mechanic. Check out all the tricky interactions between mutate, merged creatures, and everything else. The results, as the internet is wont to say, may indeed surprise you.

Questions Concerning Companion

keruga, the macrosage

It bears repeating: if you have a companion, and you only can have one, you have to reveal it before the start of each game, thereby declaring your deck to match the stated restriction. No, even a player willing to cheat can't wait and choose to cast either their 2-drop or their Keruga, the Macrosage from the sideboard.

Also note that "starting deck" refers, clumsily, to the deck you present for each game. No, you can't board in Ugin, the Spirit Dragon if you still want to cast Lurrus of the Dream-Den via companion. However, if you use Fae of Wishes // Granted to get Ugin and Ugin somehow ends up in your library, then Lurrus doesn't care.

Companions are the first cards ever legal in Standard to reference "deck" at all, breaking a wall between in-game terminology where it's always "library" and the outside world. So yes, Wizards should have used even more tournament terminology here and just write "presented deck" instead. "Starting deck" needlessly confused many people, including the most notable of Magic experts such as, oh, our current World Champion.

Unrelated to Companion or Mutate

gyruda, doom of depths
  • When you target an opposing Narset, Parter of Veils with Inspired Ultimatum, Narset remains on the battlefield until the Ultimatum has finished resolving. Only then do state-based actions put the loyalty 0 planeswalker into the grave. This means, you don't get to draw any cards.

  • For Kinnan, Bonder Prodigy to generate extra mana, the permanent you tap for mana must have a mana ability featuring the tap symbol. Kinnan doesn't notice when Urza, Lord High Artificer taps an artifact and tapping Heritage Druid for its own ability doesn't count either.

  • Gyruda, Doom of Depths's triggered ability allows you to select a creature from among the eight milled, regardless of whether the cards hit the graveyard or go to another public zone instead. While Grafdigger's Cage and Kunoros, Hound of Athreos stop this effect, Rest in Peace and Leyline of the Void do not. When Rest is in play, Gyruda simply takes a creature from exile. In fact, when Rest is in play, Cage and Kunoros no longer work to prevent any of this and you could even mill, exile, and reanimate a Progenitus you own.

  • Stonecoil Serpent is a neat way for a deck accompanied by Lurrus of the Dream-Den to spend more than two mana on a creature. But once Lurrus is in play and the X spell in your graveyard, the Cat Nightmare only allows you to recast a dead Serpent with X=2. Note the difference in wording and functionality to Chandra, Acolyte of Flame. Also note that Lurrus does allow you to cast Rix Maadi Reveler from your graveyard for its spectacle cost.

Be aware that several of these interactions may not work correctly on digital platforms such as Magic Online.

Massive Mutant Merging

Brokkos, Apex of Forever - Gemrazer - Illuna, Apex of Wishes - Pouncing Shoreshark - sea-dasher octopus - Snapdax, Apex of the Hunt - Vadrok, Apex of Thunder - vulpikeet


When you choose to cast a creature spell using mutate, some very interesting things happen. First, you need to select a target. The target has to be a non-Human creature and it has to be owned by the same player who also owns the mutating creature spell. The first limitation seems to be purely flavorful; Humans just don't mutate. The second, targeting a creature with the same owner, is important for how mutating cards behave on the battlefield, specifically for how they leave the battlefield. Note that the cards themselves remind you to pick a "non-Human creature you own," which isn't technically correct. If you cast your opponent's Gemrazer via Mnemonic Betrayal and want to mutate, you cannot actually target a creature you own.

Then, you're paying an alternative instead of the card's casting cost. Whenever you do so, you have to pick one of the alternatives available to you. This means, Fires of Invention doesn't allow you to mutate for free. It is the same reason why Snapcaster Mage targeting Force of Will requires you to spend five mana on the flashback. However, effects like that of Umori, the Collector — if set to creature — or Spellwild Ouphe — if targeted itself — still apply and influence the total you have to pay. Neither alternative ways of casting nor cost modifiers affect a spell's converted mana cost. Disdainful Stroke can counter Gemrazer whether it's mutating or not.

So now you have a spell on the stack that is a creature spell and has a target. This is a first in Magic and creates a whole new spectrum of ways for players to interfere. Your spell is fair game for Essence Scatter as well as for Misdirection. It's also possible to make the target "illegal" before the spell resolves: for example, the target leaves the battlefield, ceases to be a creature, becomes a Human, gains protection from a relevant color, or gains shroud. If an instant or sorcery has at least one target and if all of its targets have become illegal by the time it's trying to resolve, then it does nothing and moves into its owner's graveyard. The same isn't true for your mutating spell. If its target is illegal when the spell resolves, the card simply enters the battlefield as a regular creature, ignoring all the mutate shenanigans.

But if your mutating spell resolves with its target still legal, then you have to "merge" the card with its target. How you merge is a decision you take upon resolution; you don't have to announce your intention or even make up your mind beforehand. It is also the topic of our next chapter.


You put the newly cast card either over or under its target. It doesn't matter if the target has merged with something else previously, as the exact position of a component in a three-way merger doesn't matter. The only thing relevant is which component is on top.

The top component gives the merged permanent all of its base characteristics: name, cost, color, card types including supertypes and subtypes, as well as power and toughness. It also determines whether the whole thing is considered a token or not. All the other pieces only add their abilities to the mix. Imagine copying the rules text from their text boxes. The one exception pertains to Commander. If a player's commander is part of a merged permanent, the whole thing is considered to be their commander.

The merged object is not a new object. Equipment, counters, and Auras remain in place, unless the new top card clashes with an Aura's enchant restriction. For example, a mutating Dreamtail Heron could make the opponent's Controlled Instincts fall off. After taking care of such "state-based actions," the game checks for possible triggered abilities. Abilities that trigger when something enters the battlefield don't, because no new object has done so. Basically, what becomes relevant here are abilities that specify "whenever this creature mutates" as their trigger. These abilities are active the first time a permanent mutates, even if this mutation only made it gain said ability.

You may already know that when a creature's ability references its own name, it simply applies to itself. It doesn't matter whether you copy Bristling Boar with Lazav, the Multifarious or mutate Gemrazer on top of the Boar. You get a creature whose name is not "Bristling Boar" yet can't be blocked by more than one creature. Mutate triggers use the wording "this creature" instead of names to avoid confusion, but there's a similar issue: it is possible that an object that just mutated isn't a creature. The mutation triggers the ability nonetheless.


Merging allows a single object on the battlefield to consist of multiple cards, though it counts, acts, and moves as one. When it dies, all cards end up in its owner's graveyard. When an effect returns it to its owner's hand or puts it into its owner's library, all cards go there. This is why mutate restricts targeting to things owned by the same player.

As usual, when multiple cards go to the graveyard at the same time, the owner can determine in which order the cards lie. Now, the same is true for effects like that of Teferi, Hero of Dominaria that move permanents to a specific position in the library. If a merged permanent moves into a library third card from the top, the owner puts all merged cards beneath the top two cards of that library. They choose the order and don't have to reveal it. Thus, you may not know the top card of a library after hitting a permanent with Aether Gust.

god-eternal kefnet - the scarab god

When a merged God-Eternal Kefnet dies or is put into exile, its owner may put either none or all pieces into the library. The Scarab God merged with other cards dying results in every piece returning to its owner's hand at end of turn. If Syr Konrad, the Grim witnesses any of this, there is one trigger for the initial death, because only one creature died, but a separate trigger for each of the creature cards leaving the graveyard.

If a merged Blightsteel or Darksteel Colossus were to be put into the graveyard, its owner shuffles all components into their library instead. If a competing replacement effect is involved, say Rest in Peace, then the owner chooses one to apply to all pieces. They can't put some part into exile and shuffle another into their library.

Abilities that trigger when an object moves from the battlefield to another public zone look back at the permanent as it existed in play. They have to, lest cards such as Minion's Return would never work at all. This is why they affect all components of a merged permanent. Replacement effects replace one event with something else happening "instead" and as the original event affected all components, so does the replacement. However, Dread/Guile/Hostility/Purity/Vigor/Serra Avatar/Worldspine Wurm have neither: they share a triggered ability, not a replacement effect, and it doesn't care whether the card was on the battlefield before. If one of these merges with something and dies, its owner shuffles just one card into their library.

Once again, the rules know one exception: if you use the Commander variant's built-in replacement effect to put your commander into the command zone instead of your graveyard/hand/library/exile, then any cards merged with it still go where the initial effect wanted them to go. They created this exception to avoid noncommanders moving to the command zone, where they'd be uselessly stuck forever. They didn't quite succeed, though, because Leadership Vacuum achieves as much regardless. Thus, we now have a 16-part combo that allows you to put your entire deck into the command zone.

As we've seen, when a merged permanent leaves the battlefield, the cards don't necessarily lose all memory of having been connected. But they definitely lose all memory of how they were connected. If an effect puts such a permanent into exile and returns it to the battlefield, all permanent cards enter the battlefield as new and separate objects. The same applies to effects that return a dying creature from the graveyard: whether it's Unholy Indenture or persist, undying or unflying, all permanent cards merged with an affected creature return on their own, each with the appropriate counter. Likewise, Etrata, the Silencer exiles all parts of its merged victim separately and puts a counter on each.

When Nissa, Vastwood Seer exiles itself, all cards merged with the Elf go along for the ride as well. Unfortunately, the ability specifies a return in transformed form. As a general rule, the game only carries out instructions that are possible to perform and ignores the impossible. So the mutate cards, none of which can transform, remain in exile indefinitely. Though this is by no means a behavior exclusive to mutate; a simple Spark Double copying Nissa would suffer the same fate.


Except for the fact that it's a token if there's a token on top, a merged permanent is treated the same way as if it were one card. Imagine you had one card that had printed on it: all the text boxes from each component and all the rest taken from the top component. This is important for the interaction of continuous effects, all of which apply on top of the mutations regardless of what came first.

For example, when you copy a merged permanent, you also copy all the abilities the original gained via mutation, just as if you've copied a single card. Likewise, if your merged permanent becomes the copy of something else, the copied values will replace everything it was before, including all abilities gained in mutation. Note the difference to how Auras interact with copying.

However, when you copy a permanent that has mutated, the copy hasn't mutated itself. The game tracks the number of times a permanent has mutated, relevant for cards like Auspicious Starrix, separately. If Mirrorweave turns all other creatures into copies of a merged Porcuparrot, only the ones that have actually mutated can tap to deal damage; others can tap, but deal 0 damage to their target.

porcuparrot - porcuparrot

Normally, when a permanent loses and gains abilities, the latest loss or gain will count. If your flier loses flying due to Mystic Subdual and you later cycle Avian Oddity to give it flying, fly it will. But, as the enchantment itself reminds us, mutating Dreamtail Heron onto a subdued flier won't make it fly and won't make it trigger. Again, the reason is that all mutations apply at the very base level. The losing of abilities applies at a higher level irrespective of which happened first.

Mutate always getting the first word in, never the last, isn't limited to outside interference. When you mutate Archipelagore onto Tarmogoyf, you can put the 7/7 as the top card. But the resulting creature will still look at graveyards for its power and toughness, because — you guessed it — the Goyf ability applies on top.

A Forest that's become a creature thanks to Nissa, Who Shakes the World is affected by an ongoing effect that makes it a 0/0 creature. Mutation cannot change this because mutation only changes the Forest at its root. What mutation does change, if you put the new card on top, is the permanent's types and subtypes. Lands with basic land types derive their mana abilities from these types. When they go missing, the permanent no longer taps for mana. So while Dryad Arbor can grow due to mutate, it will lose its mana ability in the process.

Unlike a basic Forest animated by Nissa, Ivy Elemental is in fact a 0/0 creature at its root, and so mutations can change that. It gets even better when you put a mutating creature spell on top of Polukranos, Unchained or Phantom Nishoba, which makes them, respectively, harder or impossible to kill via regular damage.

Cards that flip contribute to a merged permanent according to their current state. Notably, Erayo, Soratami Ascendant can flip while being merged to a creature. If it's on top, the permanent will be an enchantment afterward; if another card is on top, the permanent will remain a creature.

Double-faced cards also contribute to a merged permanent according to their current side. Any change from creature to noncreature again affects the merged permanent only if the double-faced card is on top. When Soul Seizer / Ghastly Haunting transforms while merged with another creature underneath, it becomes an Aura. It becomes attached, if possible, or goes to the grave, if the opponent doesn't have a creature to enchant. The Aura keeps all abilities gained in mutation, but it doesn't transfer these abilities to the enchanted creature, and it cannot use most of them, for example trample, itself. Exceptions include Porcuparrot and Parcelbeast, whose abilities you can still activate by tapping the Aura. Of course, after having attacked, the Aura is likely tapped to begin with.

soul seizer / ghastly haunting soul seizer / ghastly haunting

When Soul Seizer transforms while merged with another creature on top, nothing much happens, except that the permanent may lose flying. The rules forbid creatures from getting attached to creatures, and non-Auras don't have to worry about the state-based action that kills most permanents with "enchant creature" if they don't enchant a creature.

The vast majority of double-faced cards are Human on one side and non-Human on the other. Note though that any change in creature type, whether through transformation or other means, doesn't matter once a mutation is complete. The restriction to non-Humans just applies while casting a mutating spell.

Mutate isn't the first time two cards combine to form a single object. Eldritch Moon already gave us meld. Thankfully, interaction between meld and mutate is minimal. You can put a mutating creature spell on top of or under Gisela, the Broken Blade; neither affects future melding. But mutating a creature spell on top of Bruna, the Fading Light precludes future melding since the permanent doesn't have the correct name anymore.

gisela, the broken blade bruna, the fading light brisela, voice of nightmares

When it's time to meld, two permanents take a trip to exile, but only the melding cards have a return ticket. Other cards merged with them stay in exile. Mutating onto Brisela afterward should not require a judge. Maybe a Flavor Judge.

A face-down permanent is, by default, a colorless 2/2 creature without rules text. For a merged permanent, the top component determines whether it's face down or face up. You can only turn face-down permanents face up, and only if there's no manifested instant or sorcery involved. These three rules translate into two scenarios:

  1. If you put a mutating creature spell under a face-down permanent, the merged permanent is still face down and, consequently, a colorless 2/2 creature without rules text. You can use a built-in option or some other way to turn it face up, unless you merged with a manifested instant or sorcery. Once face up, mutations apply to the merged permanent.

  2. If you put a mutating creature spell on top of a face-down permanent, the merged permanent is face up. It takes its abilities and characteristics from the newly cast card right away. The face-down component doesn't contribute anything and you can't turn it face up because the composite permanent already is face up.

However, it is also possible to turn a merged permanent face down, for example when it contains a face-up Wall of Deceit or Skittish Valesk. Ixidron does the the trick even when the top component and thus the whole creature is face down already. The one thing that can stop Ixidron are double-faced cards. Whether they sit on the battlefield alone or merged with another card on top or underneath, such a permanent can never turn face down. But when a merged permanent does turn face down, all face-up components turn face down; following that, you can turn the permanent with all of its components face up if you find a way to do so; and it doesn't matter which of its components, if any, contributes such a way.

Another interesting interaction concerns Sarkhan the Masterless. His +1 ability turns your planeswalkers into Dragon creatures, which means you can mutate onto them. Whether you place a mutating creature spell on top or underneath doesn't change the immediate outcome at first. The merged creature has all the abilities granted to it by the mutation and retains the original planeswalker's abilities. It also has flying, is red, a Dragon, and 4/4. The creature cannot escape this color/type/size, at least not by mutating, because, as usual, mutating works at the base. Sarkhan's effect overwrites that base — until end of turn.

When Sarkhan's effect ends, it becomes highly relevant whether you placed the creature or the planeswalker card on top. If the planeswalker card is on top, the permanent goes back to being a planeswalker. The planeswalker keeps the abilities gained in mutation. Many of the possibilities here, such as double or first strike, flying, menace, trample, vigilance, or "whenever this creature mutates," are useless until something turns the planeswalker back into a creature. Some others are useful. A Tamiyo merged with Porcuparrot can tap to deal 1 damage. A Jace merged with Parcelbeast can tap to look at and move the top card of your library. On noncreatures, these abilities even work during the permanent's first turn cycle on the battlefield. Less cute, a Chandra merged with Nethroi, Apex of Death deals deathtouch damage and gains life in the process.

If the creature card is on top, the permanent will remain a creature after Sarkhan's effect wears off. It has all the abilities from the creature card and all the abilities from the planeswalker card. It doesn't lose any of its loyalty counters when damaged and doesn't die when it loses its last loyalty counter. These rules only apply to a planeswalker, which the permanent is not. The creature can still activate loyalty abilities, one per turn, during its controller's main phase, while the stack is empty. This rule is not specific to planeswalkers.

klothys, god of destiny

Our final destination for this article is Klothys, God of Destiny — purely as an example; the following works the same with all Gods from all sets set on Theros. Let's assume our devotion to red and green is seven, so Klothys is a non-Human creature. So we can target it with, let's say, Archipelagore. When we merge and put Klothys on top, an ability triggers, but the creature doesn't change much.

When we put Archipelagore on top, something most curious happens. At the base level, we now have a nonlegendary blue 7/7 Leviathan creature with a couple of triggered and two static abilities. However, at a higher level, one of the latter interferes. It makes the permanent not be a creature as long as our devotion to red and green is less than seven. As luck would have it, our devotion has just dropped from seven to five, because the permanent previously know as Klothys now goes by "Archipelagore" and has a mana cost without any red or green in it. So the permanent is not a creature. But it isn't an enchantment either, because a merged permanent takes its card type only from the top component. So what is it?

Well, once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth: The permanent has no card type at all. It proceeds to sit on the battlefield until such a time our devotion to red and green reaches sufficient levels again. It's still indestructible, but a legal target for Boomerang and a possible victim of Urza's Ruinous Blast. Its one ability also continues to trigger at the beginning of our precombat main phase. As for the other triggered ability, which says "whenever this creature mutates"— As mentioned some 2,500 words ago, the game puts the ability onto the stack following the mutation, regardless of whether "this creature" is a creature or not, because "this creature" really only means: this … thing.

Curtain Call

I wish to express my gratitude to Guy Baldwin, a very nonjudgmental judge who painstakingly proofread this article, patiently provided answers to all of my questions, and came up with questions I never thought of asking. He also endured frequent interjections of, "But what about Porcuparrot?"

P.S.: If you were to replace Archipelagore in the Klothys scenario with Porcuparrot on top, the typeless permanent could also tap to deal 1 damage to any target.

Opinions expressed in this article are those of the author and not necessarily Cardmarket.


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Wils2189(2020-05-27 10:13)

I haven't managed to find an obvious answer for this one yet: If I cast Archipelagore for it's mutate cost targeting a creature I own that has already mutated three times. Does Archipelagore count these instances plus the one for itself therefore tapping down four creatures or is it just one because its the first time Archipelagore itself has mutated?

DvdLinden(2020-05-05 10:10)

Thank you, very insightful!

Tatzelwurm-V(2020-05-04 18:30)

Very useful informations regarding these new mechanics, indeed, thanks for that! Especially for Mutate with its texture to merge several permanents into one (there was Melding in Innistrad, true, but had much more restrictions for example only certain cards for certain combinations).

And now with the proof that there can be permaments with no card types in Magic it is not impossible to change the design of (noncreature) tokens, namely that, if they are not creatures, they do not must have a known permanent type (Food Token are artifacts, i thought Eldraine is a fairytale not the modern world?) besides Token! :)

benny-benny(2020-05-04 10:21)

Nice article.
What happens if u mutate onto a creature you own and control, but on the stack ur opponent gets control of the creature ure mutating onto? E. G. A flickered agent.

TobiHenke(2020-05-04 11:05)

Benny-benny - Control doesn't matter for mutating, neither while picking targets initially nor while resolving the mutating spell. You can mutate onto a creature your opponent controls as long as you own the target. A control change between casting and resolving doesn't affect this.

TobiHenke(2020-05-04 16:50)

Benny-benny - If your opponent gains control of the mutating spell via Aethersnatch, then they can still only pick a creature you own as the new target — because the owner of the mutating spell and its target always have to be the same. But at least they get to decide what to put on top in this scenario.

MaeseCrochets(2020-05-04 09:39)

Brilliant. Thanks for such a comprehensive article.

Rheibe(2020-05-04 09:21)

Thank you, very useful information.

Mentioned Cards