Abilities and layers

Let's assume that there's a Urborg, Tomb of Yawgmoth on the battlefield, and it's enchanted with a Guardian Zendikon.

Effectively, Urborg will now be like this:

Its full type line will be: "Legendary Land Creature - Swamp Wall". (It's a swamp because of its own ability, and this gives it the ability to tap for one black mana.)

Now let's assume that someone enchants it with Lignify.

Thus it ends up effectively looking like this:

Question: Are all lands swamps in addition to their other types?

One could hastily think that they are not, because Urborg does not have that ability anymore. However, as is usual in this blog, it's not that simple.

Urborg's ability is a type-setting ability, while Lignify's ability is an ability-setting (or in this case an ability-removing) ability. These are evaluated on different layers.

The status of all permanents on the battlefield is evaluated one layer at a time, starting from the first one.

In this situation layers 1 to 3 have nothing special to them. However, when we get to layer 4 (the layer where type setting abilities are evaluated), we see that Urborg has an ability that sets the type of each land to Swamp.

It's important to understand that at this point Lignify's ability has still not been evaluated (because its effect happens on layer 6.) Therefore at this layer Urborg still has the ability "Each land is a Swamp in addition to its other types." This is evaluated now, and therefore it sets the type of all lands to Swamp (including Urborg itself.)

Then, when we evaluate layer 6 we see that Lignify is removing all of Urborg's abilities. Thus it affects Urborg only. (Remember that so-called dependent abilities are evaluated only when they happen on the same layer. Therefore Lignify's ability has no effect on layer 4.)

Also note that even though Urborg is a Swamp due to its own ability, it does not have the ability to tap for one black mana, because Lignify is removing it.

Likewise Lignify is removing the "Defender" ability set by Guardian Zendikon, due to Lignify having a newer timestamp. (Urborg could now freely attack.)

Raging Rivers

Here's a Raging River:

The Oracle text for the card is the following:

Whenever one or more creatures you control attack, each defending player divides all creatures without flying he or she controls into a "left" pile and a "right" pile. Then, for each attacking creature you control, choose "left" or "right." That creature can't be blocked this combat except by creatures with flying and creatures in a pile with the chosen label.

This makes gameplay interesting. Basically the battlefield is divided into two, and ground creatures (without flying) can only attack and defend on one half of it.

Question: What happens if there are two Raging Rivers on the battlefield at the same time?

This situation is a bit complicated. While it's not explicitly stated in the game's rules how exactly the situation should be handled, it can nevertheless be deduced unambiguously from how effects work.

To analyze this situation, let's assume that there are six Grizzly Bears attacking and six Civic Wayfinders defending. (It's not all that important what the creatures are for the sake of this example.)

When the bears attack, both Rivers will trigger, but they will resolve one at a time. When the first River effect resolves, the attacking and defending creatures may have been divided into "left" and "right" groups for example like this (you can click on the image to get a larger version):

I have color-coded the effect of the first River with yellow markers for clarity. What the effect in question is doing is creating a continuous effect (during this combat phase) that imposes a restriction on which creature can block which other creature: Those creatures marked with a yellow L can only block those attacking creatures with a yellow L, and likewise for the yellow R markers.

Now the effect of the second River resolves. All creatures are now independently divided into "left" and "right" groups due to this effect. I have color-coded this second effect with purple markers. They could be divided, for example, like this:

The second effect likewise now states that only creatures with a purple L can block attacking creatures with a purple L, and likewise for the purple R.

The division into two groups for the second (purple) effect is completely independent of the first (yellow) effect. However, both effects are still imposing a restriction on which creature can block what. Both effects have to be taken into account when declaring blockers. For example, even though the second effect would allow a creature with a purple L to block an attacking creature with a purple L, the first effect will be restricting that possibility if they have a different yellow marker.

Therefore the only possible way to declare blockers is like this:

So, quite flavorfulwise, two Raging Rivers will divide the battlefield into four parts, and all non-flying attackers and blockers will be restricted to one of those parts. It's like a river that splits into two, and there's a mountain range between them.

The complexity of basic lands

One could find a bit of irony in the fact that basic lands are both the most ubiquitous and simplest types in Magic the Gathering, yet at the same time there's a great deal of hidden complexity behind them. (The complexity does not come from basic land cards themselves, but from the concept of "basic land type," which has a good amount of implicit rules behind it.)

Assume that Urborg, Tomb of Yawgmoth and Blood Moon are on the battlefield at the same time. What happens?

If you remember from my previous posts, or as you may already know, if an effect sets, for example, the creature subtype of a creature permanent to something, it will only replace the existing creature subtypes of said permanent and nothing else. (It will not affect any other types or supertypes the permanent might have, eg. if it's an Artifact or it's Legendary, nor will it affect the subtypes of other types, such as it having a land subtype. More importantly, though, it will not have any effect on any existing abilities or other characteristics of the permanent.)

These two cards do not set the type of lands to anything. They only set their land subtype (to Swamp and Mountain respectively.) However, these are basic land subtypes, and this is governed by special rules: If an effect sets the subtype of a land to one of the basic land subtypes (ie. Forest, Plains, Mountain, Swamp or Island), that land will lose all of its existing land subtypes and all of its existing abilities (unless the effect says "in addition to its other types") and gains the ability of tapping for one mana of the respective color. The loss of existing abilities has quite radical implications when anything sets the land subtype to that of a basic land.

To take a simpler example, consider a Sulfurous Springs enchanted with Lush Growth.

What happens here? Lush Growth is setting the land subtypes of Sulfurous Springs to Mountain, Forest and Plains. This means that it loses its existing abilities (which means you cannot tap it for colorless mana nor for black or red mana and taking 1 damage) and gains three different abilities: The first ability to tap for one red mana, the second to tap for one green mana and the third to tap for one white mana.

(Note that while Sulfurous Springs now has basic land subtypes, it's not itself a basic land. "Basic" is a supertype, and Lush Growth does not grant it.)

Before we go to the question at the beginning, consider the situation where these latter two cards are on the battlefield, and in addition there is also a Blood Moon (which says that "nonbasic lands are Mountains.") What happens?

This is a situation where we have two type-setting effects on the same layer (layer 4) affecting the same permanent. Therefore it's a question of timestamps. In other words, the answer depends on which happened first, Blood Moon entering the battlefield or Lush Growth enchanting Sulfurous Springs. The one that has the newer timestamp trumps the other.

So now to the original question: What happens when both Urborg, Tomb of Yawgmoth and Blood Moon are at the same time on the battlefield? Are nonbasic lands Swamps (in addition to their existing types) or Mountains (with no other types and abilities)? Are they both? Are basic lands Swamps in addition to their own types?

It may sound at first like this is also a question of timestamps, ie. that it depends on which one entered the battlefield first. However, there's a crucial difference here: Urborg is itself a land, so Blood Moon is also affecting it. (If Blood Moon sets Urborg's subtype to Mountain, it loses all of its abilities, which means it will not make anything a Swamp.)

This is a rarer situation where there are dependent effects on the same layer. This is a special exception to the timestamp rule which states that if the text or existence of one effect on a layer would depend on another effect on the same layer, the affecting effect is evaluated before the affected one (regardless of timestamps.)

In this particular case Blood Moon's effect is evaluated first regardless of timestamps because it modifies Urborg's effect. Therefore Urborg becomes a Mountain and loses its abilities and doesn't make anything a Swamp. (In other words, all nonbasic lands will be Mountains and all basic lands will be unmodified.)

The long history of Dragon Whelp

Some cards have withstood the test of time. Some cards that were printed in the very beginning, in the Alpha set, are still being reprinted in very recent sets. They got the card balanced enough to warrant such reprints.

It's interesting to examine how such cards have changed over time, as they often reflect the history of Magic, and how its rules and terminology have changed. One card that I find particularly interesting is Dragon Whelp. Let's examine its different incarnations (the ones that have changes from previous ones.)

This is the version printed in Alpha. The "+1/+0" boost is expressed a bit differently than it is today. Also, referring to how much mana has been spent on an ability is not something you see much in modern cards. However, the most prominent difference to modern cards is that the concept of sacrificing permanents was not yet established, and instead they were just "destroyed."

This was, in fact, the exact same destruction effect that eg. lethal damage would cause, or any spell that says "destroy." This meant that if the condition triggers and destroys Dragon Whelp, it could be saved via regeneration (a game mechanic that has existed since the very beginning.) I don't know if this was the original intent of the card's designers.

Note how the condition on mana amount has no time limit on it (ie. that the limit is only for mana spent on one turn.) This was most probably an oversight, and the original intent was for it to be only during one turn.

This is the version printed in Revised:

The maximum mana condition has now been fixed to apply to one turn only. Curiously, the "+1/+0" effect now specifies no time limit. (I'm assuming that at this point it was kind of implied that all such effects apply only until end of turn unless otherwise specified.)

Even more curiously, the creature is now "killed" rather than "destroyed" at the end of turn. This seems to be a rather non-standard term, which was quickly changed back in the next reprint.

This was printed in Fourth Edition. This seems to be the most "complete" and unambiguous wording for the pre-6th-edition terminology. The "+1/+0" is again until end of turn, and it's again "destroy."

Curiously, the third-person style of the rules text of the previous versions has been changed to a second-person style.

This is the version printed in Time Spiral. There's a quite significant change in the text, which is now much closer to modern terminology. It's now "gets +1/+0", instead of referring to spent mana it refers to how many times the ability has been activated, and it's now "sacrifice" instead of "destroy."

These are, technically speaking, functional changes. If the last part activates, it's not possible to save it anymore via regeneration (because regeneration only affects destruction effects, and sacrificing isn't one.) And hypothetically if you could activate the ability without paying its mana cost, or if you could pay it with something else than red mana, it wouldn't now make any difference (unlike in earlier versions which talked about spent mana.)

This is the most modern printed version. "At the end of turn" has been changed to the more unambiguous "at the beginning of the end step" (which makes a difference in some cases) and "this ability has been played" has been changed to the more modern "activated."

This is not, however, the most up-to-date version of the card. The rules text has been updated in Oracle, which says:

R: Dragon Whelp gets +1/+0 until end of turn. If this ability has been activated four or more times this turn, sacrifice Dragon Whelp at the beginning of the next end step.

There's a subtle difference, and not only in the order of the wording. Notice how it now says "at the beginning of the next end step." The word "next" makes a functional difference. (In practice it means that if the fourth activation happens after the beginning of the end step, it will have to be sacrificed at the beginning of the end step of the next turn. The printed version did not have this consequence.)