Welcome to a new judge article. In today's issue we will be discussion one of the more difficult topics of magic, namely layers.

Why do we have layers?

In case you did not notice, magic games can become very complex, especially when you have that *one guy* in your EDH group that decides to mess everything up.
I must admit I enjoy being that guy, but that is a different story. Over the last 20 years thousand of magic cards have been printed, and they all need to act nicely with each other.
Layers ensure that this happens by strictly defining the characteristics of a permanent and in what order effects are applied. For example, Bad Moon and Darkest Hour are both in play.
Depending on whether Bad Moon is applied before or after Darkest hour changes the outcome. Layers ensure that Darkest Hour is applied before Bad Moon, no matter the order in which the cards are played.

What are the layers?

There are 7 layers in total, with 1 layer having sublayers. Here is the list (a hint: no one knows these by heart, judges carry little papers with these layers written on them, or just use the computer):

• Copy Effects
  
• Control-Changing Effects
  
• Text-Changing Effects
  
• Type-Changing Effects
  
• Color-Changing Effects
  
• Ability Adding or Removing Effects
  
• Power & Toughness
  

The last layer has several sublayers, which we will discuss in detail later. Whenever we want to know what a permanent really looks like we step through this list and carefully apply all the effects present.
If multiple abilities take place in the same layer we apply them in time-stamp order, meaning that if two effects apply in the same layer we apply the effect that was first before the effect that came later (except when there is an exception, because it is magic after all. We discuss these later).
After processing them all we end up with the real characteristics of the card.

So, what happens in every layer?

Layer 1: Copy Effects

First of all, copy and cloning effects are applied. Did you play a Clone or Copy Enchantment? This layer makes sure that you are actually copying the card.
Copies and clones have a whole separate rule section, which I will not be discussing today. Basically, just image the other card was lying on the table instead of the clone.

Layer 2: Control-Changing Effects

Normally, a permanent is controlled by its owner. Control-changing effects change these, for example by playing Mind Control, Confiscate or Corrupted Conscience.
If multiple control-changing effects are in place we treat them in time-stamp order. In an EDH game, player A plays a Grizzly Bears. Player B plays a Mind Control on the bears, and now controls it. Player C then plays a Confiscate on the bears. As his effects comes later, he now controls it.
Later, the confiscate is destroyed. Player B is once again the controller of the bears (as his effect never went away).

Layer 3: Text-Changing Effects

In this layer cards such as Mind Bend, Alter Reality and Trait Doctoring take place. Not much to say, except that you replace all the text according to the spell.
Note that reminder text is not considered to be part of the text of the card.

Layer 4: Type-Changing Effects

In this layer we apply cards that change the type of a permanent. Examples are Urborg, Tomb of Yawgmoth, Conspiracy, Amoeboid Changeling's effect and Nameless Inversion. Once again, apply everything in timestamp order, so if you first apply amoeboid changeling to your Draco and then cast nameless inversion it will not have any creature type, while if you do it the other way around it will have every creature type.

Layer 5: Color-Changing Effects

In this layer we define the color(s) of the card. Cards like Moonlace, Painter's Servant and Darkest Hour are applied.

Layer 6: Ability Adding or Removing Effects

In this layer we look at all the abilities a card has, such as Grisly Transformation, Basilisk Collar and Turn to Frog.

Layer 7: Power & Toughness

In this layer the P&T of a creature is defined. As stated before, this layer consists out of several sublayers. In order to know the P&T of a creature, we step through these layers one-by-one.

• Effects from characteristic-defining abilities that define power and/or toughness are applied. Think of cards such as Tarmogoyf.
  
• Effects that set power and/or toughness to a specific number or value are applied. Think of cards such as Lignify.
  
• Effects that modify power and/or toughness (but don’t set power and/or toughness to a specific number or value) are applied. Think of cards such as Giant Growth.
  
• Power and/or toughness changes from counters are applied. Think of cards such as Travel Preparations, or more exotic ones like Contagion.
  
• Effects that switch a creature’s power and toughness are applied. Such effects take the value of power and apply it to the creature’s toughness, and take the value of toughness and apply it to the creature’s power. Think of cards such as Twisted Image.
  

So, when we give our grizzly bears +3/+1 and later cast twisted image it will be a 3/5 creature. If we first cast twisted image and then give it +3/+1 it will still be a 3/5 creature.
The main thing to remember is that P&T switching is applied at the very end, and all the rest feels very natural.

Dependency Hell

This is, in my opinion, the most difficult part about the whole layer system. Most of the time we apply effects in timestamp order when they are applied in the same layer. Except when this results in problems.
The most common example that happens in games is the interaction between Blood Moon and Urborg, Tomb of Yawgmoth.
Imagine a board state where Blood Moon is in play, and a player plays Urborg. Both cards apply in layer 4 (type-changing effects). Urborg adds a Swamp type to every land. Later, Blood Moon turns every non-basic land into a mountain.
This affects Urborg as well, and so its effect would be no longer in play. It feels weird that your basic forest is a Forest/Swamp, while Urborg itself is a simple mountain. The effect we are seeing here is a dependency, which is defined as follows:

An effect is said to “depend on” another if:
(a) it’s applied in the same layer (and, if applicable, sublayer) as the other effect;
(b) applying the other would change the text or the existence of the first effect, what it applies to, or what it does to any of the things it applies to; and
(c) neither effect is from a characteristic-defining ability or both effects are from characteristic-defining abilities. Otherwise, the effect is considered to be independent of the other effect.

In the case of Blood Moon and Urborg: both are applied in the same layer, applying blood moon would change what Urborg does and neither effect are a CDA (a CDA can be found on Tarmogoyf). Thus, Urborg depends on Blood Moon.
In this case we first apply Blood Moon first, after which we apply the remaining effects (if there are any). In the case of Urborg, it no longer has an effect after Blood Moon, as blood moon has turned it into a mountain.

Example Time

Example 1

Albert controls a noble Squire. Norbert is scared of this magnificent creature, and plays a Crookclaw Transmuter, targetting Squire with the ability.
After the ability has resolved he plays Hydrosurge targeting the Squire. Albert claims his survives as it now is a -3/1 creature. Norbert says it is a 2/-4 creature and should be quite dead.
Who is correct?

Spoiler:

Example 2

In the finals of a Modern GPT Alex is playing affinity versus Nessim, a Melira-pod player. Nessim has 9 poison counters, but topdecks a Melira, Sylvok Outcast and plays it. During Alex his turn, Alex activates Inkmoth Nexus.
Alex claims the Inkmoth has Infect and will kill Nessim. Nessim claims Melira removes the infect and he will take 1 damage. A judge (that is you) is called. What happens in the combat step?

Spoiler:

Example 3

In a legacy game Andre is playing the Painter's Servant Grindstone combo deck. His opponent has the ultimate sideboard tech available, namely Humility.
Does this stop the painter combo or not?

Spoiler:

Example 4

Albert has a Germ token equipped with Batterskull and a humility in play. How large is the token, and does it have vigilance and lifelink?

Spoiler:

Example 5

A classic layer question is the interaction between 2 Opalescences and Humility. What are the possible outcomes?
Note the following: This is the current interaction between Humility and Opalescence:The type-changing effect applies at layer 4, but the rest happens in the applicable layers. The rest of it will apply even if the permanent loses its ability before it's finished applying.

Spoiler:

So, that concludes today's topic on layers. I don't know yet what I will discuss next time, but I'll come up with something .
As always, if you have questions (or you spot an error, which is very likely) do not hesitate to contact me.

there is a mistake in your example

reinout a écrit:Imagine a board state where Blood Moon is in play, and a player casts blood moon

hotshot162 a écrit:there is a mistake in your example  

reinout a écrit:Imagine a board state where Blood Moon is in play, and a player casts blood moon

you've never seen the double blood moon, it's very complex
thanks, it has been updated.