Hic sunt dracones!
What follows deals with a topic that is very complicated and definitely not required for a judge candidate. If you are studying for your test, we suggest you to skip to the next page. If you are already certified and want to enlarge your knowledge, proceed at your own risk.


With over eleven thousand cards and counting, Magic sports a great variety of effects. When these effects are continuous, they interact with one another in ways that may not always be intuitive or easy to understand. If you're a judge or have been thinking to become one, you probably don't need to be reminded of this card:

Mark Rosewater recounts that, after designing Humility, he was really satisfied of his creation, that he deemed simple and easy. And it really is, by itself. The pain begins when Humility interacts with other cards.

For years, rulings were handled on a case-by-case basis by Stephen D'Angelo, a rules guru that wasn't even affiliated with Wizards of the Coast.[1] When Sixth Edition was released, the rules faced a major reworking, with the creation of that fine document that are the Comprehensive Rules; this update introduced a system to handle the interaction of continuous effects that - albeit with several tweaks - is still in use today, and tries to held results that are, in this order:

  • univocally determined;
  • similar to what a player would intuitively guess;
  • akin to the "pre-revisionist" rulings.


This system classifies all possible effects in seven categories, known as layers, and specifies the order in which these categories should be evaluated. We'll discuss in detail these categories and see what goes in each, since properly dividing effects among them is paramount for correct interpretation of difficult board states.

Other rules specify the relative order of effects within each layer. Generally speaking, effects that provide values usually printed on cards are applied first, then other effects follow in the order they were generated - with an important exception in case they interfere with each other.

The target of this very long set of rules is to order all the continuous effects that could coexist. After doing this, the actual calculation of the results they yield is trivial.

The layers

Each continuous effect belongs in exactly one of the following layers (and, if applicable, sub-layer). If an effect does more than one thing, it has to be split and the single parts applied in the appropriate layers.

  1. Copy effects
  2. Control-changing effects
  3. Text-changing effects
  4. Type-changing effects[2]
  5. Color-changing effects
  6. Effects that add or remove abilities
  7. Effects that alter power and/or toughness
7a. Effects from characteristic-defining abilities
7b. Effects that set power and/or toughness to a specific value
7c. Effects that increase or decrease power and/or toughness
7d. Effects from counters
7e. Effects that switch power and toughness

Copy effects

Copy effects are easy to spot: they always use the word copy, and only these effects use this term. Copy effects have very specific rules on what their result will be; at this time, it's important to note that some effects copy an object with some exceptions, whereas others copy an object and then further modify the copy. The two should not be confused: exceptions to a copy effect are part of the copy effect itself, and are applied with it in the layer 1; further modification go in the appropriate layer. Effects of the first kind can be recognized because they use the word except.

Example. Quicksilver Gargantuan copies a creature, except it's still 7/7. This is a copy effect with an exception, so it's all applied in layer 1. If Clone enters the battlefield as a copy of a Quicksilver Gargantuan that is copying something else, Clone will be 7/7.

Kiki-Jiki, Mirror Breaker, on the other hand, creates a copy of a creature and then gives the token haste. If a Clone becomes a copy of the token, it will not have haste.

Control-changing effects

These effects change who controls a given permanent. There's not much to say, except that effects that put onto the battlefield stuff under a player's control are not control-changing effects.

Example. Mind Control changes the controller of a permanent when it's already on the battlefield, so it's applied in layer 2. Gather Specimens, on the other hand, causes the creatures it applies to to enter the battlefield already under somebody else's control, so if not handled using the layers system.

Text-changing effects

These effects alter the text of a card, defined as its rules text plus its type line. These effects always use the words change the text, and never affect names or mana symbols. Note that abilities granted to permanents are not present in their text box, so can't be affected by text-changing effects.

Example. A Circle of Protection: Black on the battlefield is targeted by Mind Bend. Upon resolution, the devious blue mage changes "black" with "green", which allows him to prevent damage from the menacing Force of Nature he's facing. Targeting the mighty Elemental with Mind Bend has no effect, since the Manag.gifManag.gifManag.gifManag.gif cost it requires as an upkeep is not affected.

If a Pithing Needle enters the battlefield and CoP: Black is chosen, the mind-bent enchantment can't be activated, since its name was not changed.

If I control a Benalish Hero enchanted by Black Ward, and you target my creature with Mind Bend to change "black" with "green", nothing happens, since granting protection to the Hero does not change its text, but only its abilities. (Targeting the Black Ward, of course, will have the intended effect.)

Type-changing effects

All effects that change or grant additional types, subtypes or supertypes to permanents fall in this category. These effects are quite common: several cards alter supertypes (Leyline of Singularity), types (Nature's Revolt) or subtypes (Dralnu's Crusade). They also come with enough rule baggage that we have devoted them a whole page. There are a couple of points that are worth calling back to here:

  • If an effect changes a land's type to one of the basic land types, this has the side effect of stripping the transformed land of all abilities printed on it. These abilities are lost in layer 4.

Example. I have a Yavimaya Coast enchanted with a Squirrel Nest when Blood Moon enters the battlefield. Yavimaya Coast loses the abilities generated by its printed text (so I won't be able to add Manau.gif, Manag.gif or Mana1.gif to my mana pool) and gains the intrinsic mana ability of Mountains (so I will be able to draw Manar.gif from it). Since the ability granted by Squirrel Nest will be gained in layer 6 (and it's not generated by the land's text anyway), I will be able to tap it to generate a Squirrel.

  • Sometimes, an effect tries to give a permanent a creature type at a time it is not a creature. If this happens, the effect does nothing. Note that we need to evaluate if the permanent is a creature at the time the effect tries to apply in the context of the layer system; it's not enough that the permanent will be a creature after all effects have been taken onto account.

Example. I activate Gideon Jura's third ability to turn it into a creature and attack. My opponent activates Olivia Voldaren's first ability to kiss it and turn it into a Vampire (the 1 damage is prevented, but the type-changing effect does not depend from successfully damaged the creature). Gideon is now a Vampire Human Soldier, and my opponent can gain control of it if he can afford to spend Mana3.gifManab.gifManab.gif. At the end of turn, it stops being a creature, so Olivia's effect stops turning him into a Vampire.

Color-changing effects

Guess what? These effects change the color of the affected permanent. Remember that portions of other effects that change colors fall here, and that if you have to choose a color, you must choose from among white, blue, black, red, green and purple. You can't choose stuff like "colorless", "artifact", "Elf", "Tex", and other such frivolities. ,

Effects that add or remove abilities

Effects that say that a permanent gains an ability, has an ability, or use the word with - as in "becomes a creature with flying" - are adding abilities to that permanent. Effects that say that a permanent loses an ability or make it into a permanent with no abilities are removing abilities.

Note that if a permanent has multiple instances of the same keyword ability (redundant or not) and an effect removes that keyword ability, it removes all instances.

Effects that alter power and/or toughness

Since creature combat is the focus of the game, there's a great number of effects that grow or shrink creatures. For this reason, effects that fall inside this layer are not ordered as in the other layers. Instead, they are distributed among five sub-layers; within each sub-layer, the aforementioned rules for ordering apply.

Effects from characteristic-defining abilities

Characteristic-defining abilities are a class of static abilities that's defined very strictly. Those abilities define values that are usually flat-out printed on the card, usually in order to have them vary during the course of game play.

A characteristic-defining ability is an ability that respects all the following requirements :

  • It defines a characteristic, such as color, subtype, power or toughness.
  • It's intrinsic to the permanent. This means that it's printed on the actual cardboard, granted to a token by the very same effect that creates it, or gained by means of a copy or text-changing effect. The abilities granted by any other mean are not intrinsic, not even when an object grants an ability to itself.
  • It only affects the characteristic of the object it's on.
  • It's not conditional. Abilities that work only when some condition is met are not welcome here.

Characteristic-defining abilities have an important property: they work in all zones, not only from the battlefield.

Example. Tarmogoyf has the iconic characteristic-defining ability: its power and toughness are always equal to the number of card types among graveyards, even when it's on the stack (relevant for Essence Backlash, for example) or in exile (relevant for Sutured Ghoul). Nylea, God of the Hunt's ability that sometimes turns her into a non-creature enchantment, on the other hand, is not a characteristic-defining ability, since it's conditional. It only works while Nylea is on the battlefield, so she can always be countered by Scatter Essence and targeted by Disentomb, regardless of my devotion to green.

Effects that set base power and/or toughness

These effects simply state that the base power and/or toughness of a creature become a certain number. These effects are generated by abilities from non-creature permanents that "animate" and become creatures (Jade Statue, Mutavault), by static abilities (Humility, Gigantiform), or by resolving objects (Sorceress Queen, Humble). We don't care about the source: if it sets the values, it goes here.

Effects that increase or decrease power and/or toughness

This layer includes effects that raise or lower power and/or toughness, such as Giant Growth, Nameless Inversion, Crusade, Mutilate, Looming Shade and countless others.

Example. Erg Raiders is enchanted by Unstable Mutation and I activate Sorceress Queen targeting it. The effect from Sorceress Queen is applied in layer 7b, since it sets power and toughness to a certain number; Unstable Mutation increases them, so it gos in layer 7c:

7a: -
7b: Erg Raiders becomes 0/2
7c: +3/+3, so it becomes a 3/5
7d: -
7e: -

The Erg Raiders ends up as a massive 3/5.

Effects from counters

Counters increase or decrease power and toughness, so there's no reason to segregate them here. I guess we'll just have to deal with it.

Experts only! Actually, there is a corner case where having +1/+1 counters segregated in their own layer is relevant. It involves a Phyrexian Ingester that ate good ol' Skullbriar, the Walking Grave - the details are left as an exercise for the reader.

Effects that switch power and toughness

These effects always use the word switch.

Example. Windreaver is on the battlefield with a +1/+1 counter on it. Its controller attacks with it, activates its third activated ability twice, casts Giant Growth on it and then activates its fourth activated ability, hoping to deal massive amount of damage. After all this stuff resolved, the defending player casts Humble on the not-so-humble Windreaver. How does it look like now?

We always start by distributing the effects in the appropriate layers, then we apply them on the original object. In this case, they all modify power and toughness, so they all live in layer 7. The counter goes in 7d, the +0/+1 activations in 7c, Giant Growth in 7c as well, the switch in 7e and Humble in 7b. So:

7a: -
7b: Windreaver becomes 0/1
7c: +0/+1, +0/+1, +3/+3, so it becomes a 3/6
7d: +1/+1 from the counter, so it becomes a 4/7
7e: switch, so it becomes a 7/4

The Windreaver ends up as a massive 7/4 - probably not what the defending player was hoping to obtain!

Effects that span several layers

Sometimes, a single effect can be divided into smaller chunks, each of which would fall into a different layer. In this case, we treat it as though each portion was a stand-alone continuous effect, with a very important difference: once an effect has started applying, all of its parts will apply in the appropriate layer, even if the ability that generated it is removed during the way.

Example. Natural Emergence has a static ability that generates a complex effect, that can be divided as follows:

4: Lands you control become creatures
6: Those creatures gain first strike
7b: Their power and toughness are set to 2

Now, let's suppose Humility and Opalescence are on the battlefield. This notorious combo will make Natural Emergence a creature, and Humility will strip away its abilities. What do the animated lands look like?

4: Lands you control become creatures, Natural Emergence and Humility become creatures
6: Lands-turned-creatures gain first strike, all creatures lose all abilities
7b: Lands-turned-creatures' are set to 2/2, Natural Emergence and Humility are set to 4/4, all creature become 1/1

Since the effect from Natural Emergence started applying in layer 4, before being removed by Humility in layer 6, all parts of it will apply. Even though in layer 7 its source ability is long gone, it will still apply. The actual results of this derelict situation depends on the order we apply effects in the same layer, which is the matter of the next paragraph.

Order within layers

Layers are useful to sort effects of different nature. However, similar effects fall into the same layer, and we need to establish a way to order those as well. In a pinch, we apply the following rules:

  • Effects from characteristic-defining abilities are always applied first
  • Then, dependent effects are ordered so that each dependent effect is applied after all effects it depends on
  • Then, independent effects are applied in timestamp order

Effects from characteristic-defining abilities

Characteristic-defining abilities are a class of static abilities that's defined very strictly. Those abilities define values that are usually flat-out printed on the card, usually in order to have them vary during the course of game play, and work in all zones, not only from the battlefield. We already talked about them above.

Dependent effects


Let's suppose you have Crusade on the battlefield; then, your devious opponent casts Celestial Dawn. Your opponent's creatures are now white, but do they receive the +1/+1 bonus from your Crusade?[3] After all, they weren't part of the crusade in the first place...

Sometimes, an effect can influence an other, changing:

  • the existence of the first effect
  • what it applies to
  • what it does to any of the things it applies to

If both effects apply in the same layer, and neither is a characteristic-defining ability, the second effect depends on the first.

Let's provide an example for each of these possibilities:

Example. Humility erases the ability on Lord of Atlantis, so the effect that gives Islandwalk to Merfolk depends on the effect of Humility that removes abilities, as it changes the existence of the former. On the other hand, note that the effect that gives Merfolks +1/+1 does not depend from the effect from Humility that makes critters 1/1, since they apply in different sub-layers.

Example. Conversion turns Mountains into Plains. Then an Island is targeted by Mystic Compass, and the artifact's controller chooses to turn it into a Mountain. Conversion's effect will start applying to it, so it depends on Mystic Compass'.

Example. Necrotic Ooze and Yixlid Jailer are on the battlefield, and Triskelion is in my graveyard. Applying Necrotic Ooze before Jailer will not change what Jailer's effect does and what it does it to, so Jailer is independent from Ooze.

Applying Yixlid Jailer before Ooze will not change the existence of its effect, nor what it applies to. However, it modifies what Necrotic Ooze's effect does to the object it applies to (Ooze itself): instead of gaining Triskelion's activated ability, it won't gain anything, so Necrotic Ooze depends from Yixlid Jailer.

Sometimes, you may have effect A that depends on effect B, B that depends on C, and C that depends on A. In this case, we have a dependency loop, and we apply the Ostrich algorithm:[4] we outright ignore the loop, and treat these dependency relationships as though they didn't exist.

We now know to tell dependent effects.[5] We can now use this to order depending effects, and this is how we do it: when an effect depends on one or more other effects, it is always applied after all the effects it depends on.

Timestamp order

When there is no dependency among effects, we simply apply them in the order they were created. This is usually very simple, but we may need a formal definition of the timestamp each effect receives. The simplest version of the rule can be laid out as follows:

  • The timestamp for continuous effects generated by resolving spells and abilities is the time the source resolved.
  • The timestamp for continuous effects generated by static abilities is the time the permanent with the ability entered the zone it's currently in.

Example. A land is both enchanted by Spreading Seas and targeted by Tideshaper Mystic's ability, choosing Plains. Both effects apply in layer 4, and neither depends from the other, so they are applied in timestamp order. The timestamp of the Spreading Seas' effect is the time Spreading Seas entered the battlefield; the timestamp of the effect from the Tideshaper Mystic's ability is the time the ability resolved.

So, if the land is already enchanted when the Merfolk's ability resolves, it will be a Plains; if the ability is activated in response to the Aura, it will be an Island. Note that the fact that one effect has a duration whereas the other lasts indefinitely is irrelevant.

There's a couple of juicy side rules regarding effects generated by static abilities:

  • If a permanent gains a static ability, the timestamp of the effect generated by that ability will be either the time the permanent entered the battlefield or the time it gained the ability, whichever is later.
  • Auras and Equipments[6] receive a new timestamp when they are moved to a new permanent or player.

Example. The young and eager Kalle has cast an Argothian Wurm and a Shivan Dragon, but the devious Dave casts a Mind Control on Kalle's Shivan Dragon. Kalle takes back his monster with Insurrection, and swings with both creatures: Insurrection has a later timestamp than Mind Control, and thus overrides it.

During combat, Dave casts Aura Finesse on his Mind Control, and attachs it to Argothian Wurm. This resets the timestamp of Mind Control, and makes it earlier than the timestamp of Insurrection, so he gains control of the Wurm, which is removed from combat.

Note that he could legally choose the Shivan Dragon as a target for the Aura Finesse, but since in this case the Mind Control wouldn't have actually moved, its timestamp would have stayed the same.


(Would you believe it's a real word? Me neither.)

This set of rules should be applied only to continuous effects that modify characteristics or control of objects. These are the great majority of the effects we usually find on cards, but a brief summary of other kind of effects is in order:

  • Some effects affect players rather objects, for example granting them protection from something. These effects are applied after the whole layer madness has been handled, according to timestamp and dependency rules. They sort of live in an imaginary eighth layer.
  • Some effects modify game rules: for example, they might change the maximum hand size for a player or state that creatures can't be blocked. These are applied after object characteristics have been calculated, according to timestamp and dependency rules.
  • Some effects affect the cost of spell and abilities. These effects have their own set of rules.
  • Some effects are replacement effects, and we talk about them somewhere else.

  1. I think.
  2. For very large values of type: we include here effects that change an object's card type, subtype, and/or supertype.
  3. Note that this is not an example of dependent effects, since they don't apply in the same layer.
  4. Which is a real technique used in computer science!
  5. Have a look at this message on MTGRules-L to understand what it takes to exhaustively tackle the problem.
  6. And Fortifications, too, you nitpicking completist!