So, you've got one aura which creates a supernatural effect, and one aura which kills magic. So I guess the question here is, do the auras interact, or does the effect only matter when one aura's edge meets another aura's source?

there is no additional interaction beyond the effects.
one is a magical effect and is thereby reduce in force by the background count (unless you want shedim to just be that awesome)
you treat it as you would any other spirit, or magical effect as noted under astral hazing.

So, you're of the opinion that if everyone hugs the fuzzy troll when the spooky-spookys come around, then they all get to feel safe?

I just wondered specifically about the deathly aura, because it's an anti-life aura, which, by definition should be an anti-mana aura, aka a mana sink.

Life persists without mana, why do believe the loss of life is intrinsically linked to a loss of mana, otherwise a fireball is also an anti-mana aura.

But, as I understand it, mana does not persist without life.
The purpose of a fireball is to create fire. The loss of life is incidental, though generally that incidental effect is what's counted on.

The thing about the whole "Death Aura" effect is that it straight up removes life, eventually all life, from its area. That is its essence.
How is Background Count supposed to effect a being (or, more appropriately, an anti-being,) whose ideal environment is without life and therefore without mana.

I'm not looking for clarification so much as interpretation.

The Astral Hazing would reduce the effects of the Deathly Aura.

Why?

Deathly Aura uses magic to power its effect. Astral Hazing reduces the magical power in the area. So if the two areas-of-effect overlapped, the Haze would reduce the power of the Deathly Aura, potentially negating it if the power of the spirit with Deathly Aura if it's Force 4 or less.

Deathly Aura, Death Touch, invoking Blood Spirits, Fireball, Physical Mask, Trid Phantasm (Groovy Rainbows of Goodness), conjuring Fluffy Bunnies of Love, and practically every other magical effect you can think of relies on the manipulation of mana. The fact that some are deadly and suck your soul bare while others are happy sunshine spells of awesomesauce makes no difference. Magic is magic, only the little details are different.

Astral Hazing, just like the background counts it creates, completely screws up one's ability to work magic in the area. Whatever it is that allows magicians and critters to manipulate mana is crumbled up into a wad of paper, set ablaze, and pissed upon to put the fire out just for good measure. If you step into a background count and try to manipulate mana -- whether it's a deadly aura that sucks your soul bare or a happy sunshine spell of awesomesauce -- it's not going to work very well.

Deathly Aura and Astral Hazing are about as related to one another as an apple is to a sledgehammer.

Alternatively, what would be the effect of Deathly Aura in an Aspected Backround Count? None, as there's no Test for Deathly Aura?

If it's aspected to a shedim's tradition, whatever that is, its effective Force would be increased just like any other power/spell/effect. None of Deathly Aura's offensive uses are based on its Force, however, so it wouldn't affect it much. The secondary effects would, though. Like the faster decay rate of plants and its range.

But if the Deathly Aura was at Force 0, it would have zero effect. Attacks, Powers, Spells, Barriers, etc all cease to have an effect if their power was reduced to 0.

I meant an Aspected Backround for the creature with Deathly Aura. I should have been more clear.

I knew what you meant when I replied.

My post was for darthmord's benefit.

I just can't seem to get my head around Shedim and BC. It's dumb. They strive to create conditions in which they will cease to function. Same with the mythical horrors. The conditions they seek to create are the exact same conditions which the books give as example of how mana warps and such are formed. I guess maybe they're just aspected to the kind of BC formed by suffering and death. I suppose that makes sense. Just seems like an oversight in the rules.

The same could be said of people IRL...

Also, don't forget the optional rule for Flexible Aspect, sidebar on page 119 of Street Magic. It could be that the conditions they are creating are already Flexibly Aspected for shedim/horrors/insect spirits.