Urborg and Blood Moon in play

[GGoober]

From Gatherer:

If Urborg, Tomb of Yawgmoth and either Blood Moon or Magus of the Moon are on the battlefield, all nonbasic lands will be Mountains, not Swamps. Urborg, Tomb of Yawgmoth will be a Mountain as well. It will have "{T}: Add {R} to your mana pool" and no other abilities.

This seems a little unintuitive for me since due to layering effects i.e. both Urborg and Blood Moon/Magus of the Moon affect the "types" layer so shouldn't this be due to a timestamp issue?

1) If Blood Moon came first then Urborg, all nonbasic lands should be Mountains AND swamps
2) If Urborg came first then Blood Moon, then all nonbasic lands should be swamps.

Unless in 1) Blood Moon's effect is applied onto Urborg while Urborg is applied in a timestamped manner but since Blood Moon causes Urborg to lose its abilities, therefore all nonbasic lands are mountain even if Urborg came later.

[cdr]

613.7. Within a layer or sublayer, determining which order effects are applied in is sometimes done using a dependency system. If a dependency exists, it will override the timestamp system.

613.7a. 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 (see rules 613.1 and 613.3); (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. Otherwise, the effect is considered to be independent of the other effect.

613.7b. An effect dependent on one or more other effects waits to apply until just after all of those effects have been applied. If multiple dependent effects would apply simultaneously in this way, they're applied in timestamp order relative to each other. If several dependent effects form a dependency loop, then this rule is ignored and the effects in the dependency loop are applied in timestamp order.

Urborg's effect is dependent on Moon's effect.

[GGoober]

Gotcha, thanks for the rule snippet.

But now this is puzzling because I understand the Humility v.s. Magus of the Moon issue via layering/timestamp but after reading the above, won't it be a dependency issue as well?

Both use the same layer, and shouldn't Magus' ability depend on Humility since Humility says that all creatures lose all abilities?



613.7a. 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 (see rules 613.1 and 613.3);
TRUE: since both Magus and Humility use the same layer

(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;
?TRUE: Applying Humility to Magus would change the existence of the first (Magus') effect on turning lands into Mountains
?FALSE: ??

and (c) neither effect is from a characteristic-defining ability. Otherwise, the effect is considered to be independent of the other effect.
TRUE: None of Humility nor Magus has CDA.

[luma]

Humility and Magus of the Moon aren't in the same layer, actually. Magus of the Moon has a type-changing effect (which is in layer 5), and Humility has an ability-removing effect (in layer 6) and a power/toughness setting effect (in layer 7b). Thus, Magus of the Moon's effect applies first, making all nonbasic lands mountains, then Humility's effect applies, removing all abilities from Magus and making it 1/1.

[GGoober]

Ah! God I got confused again, okay all this makes sense then! Thanks!