-Fanfic Idea Start-
In an era of turmoil or as the fools call it - An era of peace...
An unassuming boy was born into an unassuming family.
However, that quickly changed when the boy began to display...
Absurd capabilities.
Impacts that would normally break bone.
Down to even potentially life-ending or crippling crashes and falls would amount to nothing more than a scratch and or momentary irritation for the boy.
The boy's durability was supernatural - Even from a bender's perspective.
But it didn't end there.
His strength was capable of flinging boulders that weighed tons without much trouble - Not even a hint of Earth Bending involved.
He was as swift as a bird, and his reflexes outperformed even those of felines.
Quickly, he was designated as a freak of nature.
But, his parents had not abandoned him.
He was still human, despite the anomaly he presented.
That is... Until a truly incomprehensible fact was discovered upon the boy when examined by a healer.
The boy was not capable of being healed.
At all.
Why?
He had no Chi.
Everything living had Chi.
The essence of life - The proof of existence.
The World does not recognize his existence.
The spirits are invisible to him.
But so is he.
He, Who Is Blind To The Spirits.
He's certainly not the Avatar.
He's certainly not even the polar opposite...
How could he be?
Even the World cannot differentiate between him and an inanimate object.
As far as it's concerned - The boy doesn't exist.
However.
He is...
He, Who Is Outside The Balance.
In the far future, after the boy becomes a man and etches his Legend upon a World adamant about not recognizing him.
His unprecedented condition will be dubbed - "Heavenly Restriction".
-Fanfic Idea End-
Honestly, I think shoving a dude with Heavenly Restriction (Toji's thing) into Avatar sounds like a fun/good idea.
Nonbenders get chi-blocking... And that's it.
Oh! They got swords!
Or Technology when we get to the Legend Of Korra Era but semantics.
Someone with Heavenly Restriction is where it's at though.
He'd probably rival the Avatar (Or maybe even stronger? Though Avatar power scaling isn't my thing so I can't really tell. They don't move THAT fast to avoid a Toji flash step lol)
Whether this is actually Toji, an OC or an isekaied OC is up to you.
I am also unsure when is the best time period to shove such a character.
Whether during the ATLA Era or TLOK Era.
Personally, though, I think he'd work best in The Legend Of Korra Era.
But The Last Airbender is more hardcore, technically, so that could work too.
There really is a lot of freedom with this thing - All of them are pretty decent options whether you are going with just even throwing the actual Toji into this.
Maybe have Zuko hire him instead of that forehead bomb guy.
Though, if Zuko hires Toji then Aang's dead - So yikes lol.