It came up in a game today, where a dual natured character ran into a rather high background count. Now the rules as written in Street Grimoire says that he would take the rating as a penalty to all skill checks. This -5 made the character virtually useless in the encounter. I'm wondering if there is any way to mitigate this next time.

This is what we're presently playtesting, but I'd like some feedback.

Background Warding Foci
Developed by the dragons for use by favored dual natured servants.

Force is the amount of background count they can ignore.
Cost (Force x $10,000)
Karma to Bond (Force x3)

The cleansing metamagic? Is that still in sr5?

Yes, Street Grimiore pg. 155. Not the healthiest thing to try (base Drain Value is equal to the Background Count), bit it is doable - if you Initiate.

There is also the Circle of Cleansing Ritual (requires Cleansing; Street Grimiore pg. 127) this takes Force (Minimum of Background Count) hours to complete and reduces a positive Background Count by Net Hits rating for Net Hits + 1 hours.

But if you are playing an adept neither option is open to you.

True, but then a dual natured Adept has got to have things going for it that need a little balancing, no?

Dual Natured Adepts can use Heightened Concern or Adept Centering to be able to ignore the penalties from Background.

As a GM I would allow this to work.

Our Adept uses Adept Centering and a High Initiation (he is grade 6 currently) to abrogate Background count when necessary.

Just as long as nobody refers to "a foci" this seems a useful tool. Perhaps too useful... it might appeal to collectors of dwarf cyberzombie backpacks.
The attribution didn't come through there - who were you quoting? I've seen a house-rule metamagic technique "Limited Fading" (based on Fading - the Critter Power from Paranormal Animals Of Europe p138) which did the same thing as the DEFENDER you quoted, withdrawing (only) from the astral plane to bypass a ward, escape FAB-III, not be so vulnerable to possession, etc. There's even been a suggestion for the opposite of Deepweed (Man And Machine p123) being a drug which shuts characters out of the astral for as long as they're doped.

Major penalties like Dual Nature typically accompany major boons to keep things balanced. Ultrasound Vision is fantastic in many ways, but hey - you can't read with it (unless you know Braille) and you can't see through windows, spectacles, etc. at all. If a character encounters a situational challenge caused by the penalty side of the balance coin, and you go and slap a quick fix on it, it smells to me like a cop-out. If a character with Ultrasonic Vision was disappointed an optical magnification scope on their sniper rifle is useless to them, I wouldn't say, "pay an inconvenience tax and you can do anything you want" - I'd simply point out that there are advantages and drawbacks to every choice in character generation, play, and life itself. Maybe this session the Dual Natured character encounters a background count. Maybe next week, the team has to swim upstream through water ducts and a different character (with no athletics, strength, body dump stats, etc.) is challenged. If a player gets to flaunt their powers most of the time, it's reasonable for the story to impose their weakness some of the time. The characters surviving dystopia is what makes it rewarding.

Dual Natured Defender is found on pg 36 of the new Forbidden Arcana magic book.

Thank you

Sorry, I forgot to do the attribution.

There were suggestions that Queens jelly were bug spirits attempt/method of adapting to the background count in Chicago. Slightly off topic but another thread to pull.