BD, if You don't mind ... what to do with Yagru ?
Rename it. First. For example it can be named Doh Urgay.
Or Hkurllab.
Change it from former Oinoloth (Whatever non OG it is) to something that is EXTACLY the same in essence but under name and backstory that isn't CG stuff.
I know that You know it already, but couldn't stop myself from trying to be helpful.
Thus IF You would wish to do it such way:
"Abyss" is a place where fiends are the free ones. Long ago it was tyrranical place, like "Hell" is now ... and tainted by Chaos, unlike "Neutral Lower Planes" that remained "purest".
Long time ago Evil was unified. Under the heel of one Ubertyrant. *Insert Yagru daydreaming sounds, and after people start gouging they ears out*
Then forces of Good kicked his arse and evil-unity was forever shattered. Fiends separated into rabid dogs without leash (Demons and their realms) and rabid dogs on leash (Devils and their realm) fighting for philosophical reasons over the ruined wasteland that was left after shattering evil's unity where fev loyalist fiends still reside, unable to put their differences away ... as usual.
I apologise in advance, but it is all my mind could produce to remain as faithful to Your Yagru as I can.