I am testing a deck against the bolt thrower deck. Of course the bolt thrower doesn't have any units. A situation came up where I played a gutter runner "comes into play corrupt" and I wanted to use chillwind to uncorrupt it. But since the opponent doesn't have any units, can I target the gutter runner to make it corrupt if it's alread corrupt? My reasoning is the effect will check to see that it's already corrupt and will just fizzle out.

You need two legal targets to cast Chillwind. You could corrupt your own Walking Sacrifice/Fledgling Chaos Spawn and uncorrupt the Gutter Runners though.

Does it? If a corrupted Gutter Runners is the only unit in play and you cast Chillwind on it, it's definitely a legal play. Chillwind doesn't specify that it corrupts an uncorrupted unit.

The question is whether the corruption part counts as succeeding to get the "Then" to trigger restoring the unit. I could see that as debatable - after all, the unit is corrupted after the Chillwind effect.

From the FAQ:

If a card uses the word “then” the preceding effect must have resolved successfully before the effect following the term “then” can be resolved.

I'd say that if the first part of Chillwind doesn't actually corrupt a unit then it hasn't resolved successfully and you can't play the second part.

ChaosChild said:

By that reasoning you wouldn't be able to play a Warp lightning cannon on corrupted units either (which you can according to the faq). Granted, the wording is not exactly the same, but I'd argue that it's the same concept. That ruling demonstrates that corrupted targets are still legal targets for a corrupting effect. Thus, the "Corrupt target unit" part has resolved successfully and the "then" effect follows.

But sure, it's certainly not clear.

Not the same at all. With Warp Lightning Cannon, corrupting the unit is efectively the second part of the ability which you do after successfully playing the card. All the ruling means is that you can play the card on a unit that's already corrupted and that the unit's state is not a prerequisite for playing the card. It doesn't establish that corrupted units are viable targets for corruption effects.

In fact the FAQ specifically states that The “corrupt that unit” effect is cancelled . If you apply the same logic to Chillwind then this means that the first part of Chillwind's ability is cancelled if you play it on a corrupted unit, which by definition means that it hasn't been played successfully.

ChaosChild said:

If the corruption is cancelled, are you certain that ALSO means that it has not resolved successfully? I would interpret this section of the FAQ to refer to a case where the target of the first section is no longer a legal target (i.e. it has been sacrificed), and therefore the second section does not occur. I'm not completely clear on the exact definition of "cancel" in this game, so I could see it either way.

If it's been cancelled then it definitely hasn't resolved successfully. In fact I'd say that it hasn't resolved at all, pretty much by the definition of the words involved.

In terms of how the card is supposed to work, I think what you are saying makes sense.

I'm just saying that I don't think the use of the word "cancel" is "by definition" the same as "doesn't resolve", because of the way the game rules already use that word. Combat damage, for example, is "canceled" by toughness, but I would definitely say it still resolves and it canceled as part of the resolution. By this usage of the word cancel, I equate it more to "prevent" than "doesn't resolve". I guess I just think of "resolved" in the sense that it was used in MTG, where that meant that the targets of the spell remained valid during resolution. As people have pointed out in other places though, being able to corrupt an already corrupted unit doesn't make much sense in terms of game mechanics, and makes certain cards overly powerful or pointless.

I thought this post by Overseer Lazarus was a good description of why you can't corrupt a corrupt unit:

According to the section on Corruption on p.17, you may only corrupt an uncorrupted card. The wording is, "When [corrruption] occurs, the card's controller turns the card 90 degrees to show that is is corrupt." Also, that "a restored card is no longer corrupt." As this is worded, when a card becomes corrupted, it gains the 'corrupted' game state, and when it is restored, it loses the 'corrupted' game state. Because the rules instruct us to rotate the card when corrupted, and that a restored card is rotated back to its original orientation, and that a restored card is no longer corrupted, we're unable to make an already corrupt card "even more corrupt".

In W:I, if you can continue to corrupt the same unit, you are essentially circumventing the rule that allows a player to restore only one unit during your kingdom phase. Why would only one unit being allowed to "come back" per turn matter to me at all if I can corrupt the same unit repeatedly to Warpstone Meteor or any other effect? The corruption of a unit as a side effect or penalty immediately becomes of little consequence AND strategy if I just get my one thrice-corrupted unit back next turn, anyway. Also, cards like Meteor become even more useless than they already are if I can casually point to a corrupted card and say, "I'm corrupting him" to avoid a bad effect.