MSE 101: So You've Made a Card That Breaks Layers

Quick question: My opponent has a Dralnu's Crusade, I have a Goatnapper that they've turned into a Goat Rogue with Artificial Evolution. Now I cast Extinction naming Zombies. Does it get my Goat?


Unless you're a judge, that situation might seem hairy to untangle. Just how do we figure what order to apply these effects in? Magic's answer to this question is the Layers system, a group of rules that usually works in intuitive ways thanks to Wizards' diligence in avoiding effects that muddy the waters. As an aspiring designer though, you're going to want have more than your intuition. I've lost count of how many times I've seen an ability that's "never been done" and see that it's because it doesn't play nice with the rules. So, just what are those rules?

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Interaction of continuous effects (or, the Order of Layers)

So when you've got a load of continuous effects (static abilities and temporary effects from spells/abilities), what order do you apply them in? The first step is to divide them into the type of change the effect causes. An effect can cause changes on multiple layers, but it will do so in this order still:

2. Control-changing
3. Text-changing
4. Type-changing
5. Color-changing
6. Ability-changing
7. Power and/or toughness-changing
    7a. Characteristic power and/or toughness (*/* creatures)
    7b. Changes to base power and/or toughness
    7c. Gets +X/+X, -X/-X, etc., and changes due to counters
    7d. PT switching

Now lets run down our scenario again:
The first thing we have is a text-changing effect, changing Goatnapper from a Goblin to a Goat.
Next is our type-changing effect Zombifying all Goblins, but Goatnapper is no longer a Goblin and is unaffected.
Then the color-changing effect and power/toughness-changing effect makes the Goblins black and gives them +1/+1, but they won't get to enjoy their buff for very long.
When Extinction resolves, it sees Goatnapper as a 2/2 red Goat Rogue and passes it by to raze its zombified brothers.

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Designing With Layers

The main thing to keep in mind with layers is that each (sub)layer should only care about layers above it. A power/toughness effect can care about an ability, which is why Favorable Winds works. A copying effect can't care about who controls the permanent, which is why Volrath's Shapeshifter is a very strangely worded card these days. The vast majority of layer errors comes from making that mistake between layers 6 and 7, like "Creatures you control with power 4 or greater have flying."

Anything that doesn't fall under one of these layers can be referenced at any point. You can control all tapped permanents. You can make all creatures with +1/+1 counters on them green Mutants. There are also some tricky ones you can do like "Creatures you control with power 4 or greater can't be blocked." Notice that those creatures don't "gain" an ability, so this effect doesn't actually use the layers system.

The spoiler below goes a bit more in depth into each layer, and shows some examples of abilities enabled and disabled due to their placement in the system. If you'd rather see how we order these effects once we have multiple on a layer, read on.

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Advanced Layers
So what happens if we have multiple effects occurring in the same layer? If I have Levitation and you have Gravity Sphere, what happens? Or Blood Moon and Urborg, Tomb of Yawgmoth? Or, Garfield forbid, Opalescence and Humility?

Characteristic-Defining Abilities
Characteristic-Defining Abilities (CDAs) are a special type of static ability that are applied before non-CDAs in each layer. An ability is a CDA if it:
1) is a static ability acquired through oracle text, a copy effect, a text-changing effect, or through the effect that creates the token that has it, and not gained through other means,
2) defines the power, toughness, subtypes, or colors of the object that has it,
3) does not directly affect any other object's characteristics, and
4) is not conditional (eg,"~ is green." is a CDA but "~ is green as long as you control a creature." is not.)

Dependencies
Once you've separated CDAs and nonCDAs and you still have two or more trying to apply at the same time, you now enter one of the most complex parts of Magic rules: Dependencies.

Dependencies allow us to care about things happening in the same layer, which has some heavy hitters like "Enchantments you control are creatures" and "Creatures you control with first strike have double strike." This does allow for some fiddling in the PT layer, but thanks to counters coming after PT boosts (likely to avoid encouraging this very thing) the best effect is being able to have base PT dependent on other permanents base PT.

An effect is dependent on a second effect if applying the second effect would change any of the following:
1) if the first effect exists (losing abilities is a common way to do this)
2) what objects the first effect would apply to (changing types is a common way to do this)
3) how the first effect would affect the objects it applies to (text-changing effects are the main culprit here)

The easiest way to do this is to see what happens if you apply two effects in each order. Once we have determined an effect is dependent, it will apply immediately after the effect it is dependent on.

For now, let's look at the first two cases:

Levitation vs. Gravity Sphere
If we apply Levitation, then Gravity Sphere:
All my creatures gain flying, then all creatures lose flying.
Gravity Sphere still has its ability, it applies to the same objects, and still causes them to lose flying, so Gravity Sphere isn't dependent on Levitation.

If we apply Gravity Sphere, then Levitation:
All creatures lose flying, then all my creatures gain flying.
Levitation still has its ability, it applies to the same objects, and still causes them to gain flying, so Levitation isn't dependent on Gravity Sphere.

They will have to wait for the next step to resolve their differences.

Urborg, Tomb of Yawgmoth vs. Blood Moon

If we apply Urborg, then Blood Moon:
All lands gain the Swamp subtype, then all nonbasic lands become Mountains.
Everything checks out, so Blood Moon is not dependent on Urborg.

If we apply Blood Moon, then Urborg:
All nonbasic lands become Mountains, then Urborg is a Mountain with "T: Add R." and no other abilities.
Urborg's ability no longer exists, so it is dependent on Blood Moon.

Since Urborg is dependent, Blood Moon will apply first and erase Urborg's ability. All nonbasic lands will be Mountains, and not Swamps at all.

Timestamps
Finally, if your effects weren't dependent (or you managed to create a loop of dependent effects), we come to the ultimate tiebreaker of layers. We've got Gravity Sphere vs. Levitation. They apply in the same layer, they're both non-CDAs, and neither is dependent on the other. Now what?

First come, first served (mostly). The remaining effects are applied from oldest timestamp to newest. Objects get new timestamps whenever they change zones, become attached to a new object, transform, or turn face-up/face-down. If you would have multiple objects get a new timestamp simultaneously, you choose the order they get their new timestamps at that time.

So let's look at our first scenario one last time:

If I played Levitation, then next turn you played Gravity Sphere, my creatures gain flying, then all creatures lose flying.
-> No one's creatures have flying.
If you played Gravity Sphere, then next turn I played Levitation, all creatures lose flying, then my creatures gain flying.
-> My creatures have flying, yours don't.

And to think, it only took us 2560 words to get to this point.

Now, we've got one last rule to contend with, and it has a lot to do with that last scenario there...

Opalescence vs Humility


tl;dr - Don't statically gain abilities based on PT.

If you've got any further questions or layers snafus, post em below and I'll set em straight, and maybe stick em here in the OP if they're good!