So, I wrote up an entire response yesterday, and lost it because something was happening to the forums that was saying the host wasn't connecting...
So here is what I originally wrote (I was able to save the text, just not post it.
just checked the actual rulebook again...
Killing Hands is explicitly mentioned as being affected by background count. No arguing that it's only talking about powers that give dice pool modifiers, the book explicitly says "... and skill tests that use active adept powers such as Killing Hands or Improved Sense"
The Missions FAQ only clarifies that (for the purposes of Missions) it only applies to Skill Tests, which means it wouldn't apply to tests that don't involve skills.
Personally, I don't agree with that slight alteration, and I apply it to All Tests still, so (for example) Combat Sense adding to Defense tests would still be affected. Same thing for other Attribute-only tests, such as a lift-carry test when you're using Magic to augment your Strength.
There are two notable exceptions: Initiative and Drain. Initiative isn't a "Test" so it isn't affected. And Drain is not automatically always affected just because it is related to magic. But if you're magically augmenting one (or both) of your drain attributes, you invite the penalty.
I also make a minor exception for some specific things such as Armor: the maximum penalty on a test where the only magic is Armor would be the Armor Rating. Essentially Armor can't create a net negative from Background, the Background can only completely cancel the magical Armor bonus.
Now, addressing the recent comment by Marcus, I'm actually confused about what you find so horrifying about the wording for Background Count. I can understand some frustration about how high the ratings go, but just because the penalties exceed 6 (by any margin) doesn't make the wording horrible. You even say that applying the penalties due to Background Count is "fine and working as was intended" ... but somehow that is the same horrifying wording except for Foci?
I don't know, your phrasing and short-hand is hard for me to read.
Personally, I don't find anything confusing about the way Background Count works. Yes, the scale is probably greater than a lot of people are comfortable with, but if you are dealing with Backgrounds (on this scale) greater than 12, you are doing something pretty crazy to be completely honest.
To break down the logic, in 4th edition, Background was rated from -12 to +12 and caused a reduction in your Magic Rating (instead of just a dice penalty). This meant that the most likely levels of Background people would see was between 1 to 6 (absolute value since in the case of penalty values positive and negative are the same). This meant that a Background of 4 caused an effective reduction in your Magic Rating of 4, which was a massive hit to pretty much everything a magical character did.
So when they changed editions they decided to approach it a little differently, they made it only a dice penalty. Which to be completely fair is a much smaller penalty. So in exchange, they widened the range. Personally, I probably would have gone only up to 18 instead of 24, but in the edition change quite a few things changed from a 1 to 6 range to a 1 to 12 range, so I guess this followed suit (1 to 12 becoming 1 to 24).
Honestly, from your comments, Marcus, I get the the impression that you just feel like Background Count should only be a minor inconvenience if anything at all. It is
supposed to be a big deal. And seeing background greater than magnitude 6 means that you are venturing into a major magical sites. A penalty of only -3 is not appropriate there...