To make a distinction for context, as far as I've read, the "O9A" is also different from the "ONA" (the Wikipedia page does not make this point, I don't believe). This knowledge is all from my own readings on places like archive.org or old Stormfront posts regarding the Order, so I may still be wrong, who knows.
The ONA was a Neo-Nazi Satanist religious organization centralized in Britain that operated in Shropshire under David Myatt and Richard Moult primarily during the late twentieth century, which then disbanded around the turn of the millennia in the early 2000's, as either became disillusioned with Satanism, Moult going through a spiritual conversion to Catholicism (which then regressed back into the occult, but with no continuation back into leading the ONA as an organization, instead dabbling in its legacy a bit and eventually leaving little trace of present activity) and Myatt isolating himself greatly from all forms of political and spiritual extremism (albeit I've forgotten further details regarding his current beliefs). The Wikipedia page does have a good description of the ONA's original doctrine, like their cosmology or their talk of the aeons, so that can provide some further context regarding the specifics there. Still, I'd recommend, if anyone's interesting in reading of them, to read some of the PDFs written by Christos Beest (Moult's alias) or other ONA writers that are on sites like archive.org in order to actually comprehend their beliefs from a primary source. A final thing to mention about the ONA is that Moult released
some interesting music back in their day, too, and, even in his Catholic era after ONA's disbandment, was very musically talented (I listen to
this album of his that was produced during his Christian days often, as a matter of fact, as it sounds very pleasant to my ears. An intriguing thing to note about this album is that it uses the poetry of a British poet native to Shropshire as the majority of its compositions' lyrics, Shropshire also being where the original ONA was established).
The O9A, meanwhile, is a decentralized Neo-Nazi Satanist group that acts more as an ideology than a form of a true, formal organization. "Nexions" are groups of Niners (adherents to the O9A) within a specific location, operating locally, and can vary somewhat on their particular ideals and beliefs. However, these beliefs nonetheless carry a common theme of accelerationism, to shatter the Magian (Abrahamic) reign that rules the West in order to rebuild from its crumbling ashes a new, Aryan empire, free from what they see as Judeo-Christianity. Some nexions are focused to the internet, rather than actual, physical occultist activity, and, some, taking accelerationism to a degree of severe cruelty, in a form of occultist sacrifice by the proxy of the internet, conduct themselves as 764 does, luring their victims into committing horrible depravities. Other affiliated groups that would fall under the O9A umbrella would include Tempel ov Blood and 676. Not all modern Niners are horrible people in the sense of such absolute cruelty, so don't make that misconception (as spiritually misguided as they are in my opinion), but all "764ers" would generally be known as Niners, I believe.
Oh, and, on a final note, some Atomwaffen guys discovered the personal information of
a few members of Tempel ov Blood and they found out that the guy who originally formed ToB is being cucked by a religious Jew hahaha