If I use Xathrid Gorgon's petrifying ability on a creature, if that creature is destroyed, exiled or sent back to it's command zone in the case of a commander...say it is brought back to the battlezone, does it retain Xathrid's petrify for the duration of the game or lose it changing zones? Is it permanently a colorless artifact with defender that cannot access it's activated abilities?
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If I use Xathrid Gorgon's petrifying ability on a creature, if that creature is destroyed, exiled or sent back to it's command zone in the case of a commander...say it is brought back to the battlezone, does it retain Xathrid's petrify for the duration of the game or lose it changing zones?
The effect wore off, effectively, when the creature left the battlefield (not: battlezone). The new creature won't be affected by that effect, because it's a different object from the one that left as far as the game is concerned (C.R. 400.7). Notably, among other things, the new creature won't necessarily have defender and won't necessarily be a colorless artifact.
Is it permanently a colorless artifact with defender that cannot access it's activated abilities?
Assuming the creature didn't leave the battlefield, then it generally is, in the sense that the effects adding defender to the creature, changing its colors and types, and restricting its activated abilities will remain for as long as the creature remains on the battlefield (see also C.R. 611.2a); the effects will be active—
even after Xathrid Gorgon leaves the battlefield,
even if the petrification counter is removed from that creature (compare Xathrid Gorgon with Aven Mimeomancer), and
even if that counter can't be put on that creature (again, compare Xathrid Gorgon with Aven Mimeomancer).
Note, however, that other effects can later add abilities, types and colors to the creature (C.R. 613.6) (but even so, any activated abilities the creature gains this way still can't be activated).
does it retain Xathrid's petrify for the duration of the game or lose it changing zones?
The Petrify effect and the counter are lost when it changes zone. The creature returns to its original printed configuration.
(take note that the petrification counter doesn't actually do anything; it's only there to remind people of Gorgon's effect.)
When an object leaves the battlefield, all effects cease to affect that object and counters are removed from it.
This is generally true for any change of zone.
(unless the effect is obviously intended to be applied from zone to zone, which Xathrid Gorgon's is not)
Is it permanently a colorless artifact with defender that cannot access it's activated abilities?
Yes... as long as it remains on the battlefield!
110.1. A permanent is a card or token on the battlefield. A permanent remains on the battlefield indefinitely. A card or token becomes a permanent as it enters the battlefield and it stops being a permanent as it’s moved to another zone by an effect or rule.
Card tags are mandatory when asking questions in the Magic Rulings forum. Please check your private messages to learn how to use them. I’ve added them for this post. -MadMage
The effect wore off, effectively, when the creature left the battlefield (not: battlezone). The new creature won't be affected by that effect, because it's a different object from the one that left as far as the game is concerned (C.R. 400.7). Notably, among other things, the new creature won't necessarily have defender and won't necessarily be a colorless artifact.
Assuming the creature didn't leave the battlefield, then it generally is, in the sense that the effects adding defender to the creature, changing its colors and types, and restricting its activated abilities will remain for as long as the creature remains on the battlefield (see also C.R. 611.2a); the effects will be active—
The Petrify effect and the counter are lost when it changes zone. The creature returns to its original printed configuration.
(take note that the petrification counter doesn't actually do anything; it's only there to remind people of Gorgon's effect.)
When an object leaves the battlefield, all effects cease to affect that object and counters are removed from it.
This is generally true for any change of zone.
(unless the effect is obviously intended to be applied from zone to zone, which Xathrid Gorgon's is not)
Have a peek at rules 122.2 & 400.7 for details:
https://magic.wizards.com/en/game-info/gameplay/rules-and-formats/rules
Yes... as long as it remains on the battlefield!
RULES OF MAGIC :
http://magic.wizards.com/en/game-info/gameplay/rules-and-formats/rules