Is WoW Forever Onyxia Attunement Account-Wide?
An Onyxia attunement on one character will not unlock your alts at launch. The new raids are planned without the same traditional entry gate.
Onyxia attunement will not be account-wide when WoW Forever launches. Blizzard plans to keep it per character initially, so completing the requirement on your main will not automatically cover an alt you want to bring to the raid.
The new launch raids follow a different entry plan: the developers say a traditional attunement will not stop players from walking inside. That does not mean every part of those raids has already been explained.
Plan Onyxia access separately for each character
The distinction matters if you intend to raid on more than one class. Track access for the character you are bringing, rather than assuming the account has been unlocked by an earlier completion.
Blizzard frames the account-wide answer around launch and the initial implementation. It has not promised a later sharing feature, but it also has not declared that character-specific access can never change.
This confirms the access policy, not a complete Forever quest walkthrough. The exact prerequisites and steps need to be checked in the current version before an older Classic checklist can be treated as reliable instructions.
New raid entry is not a complete progression reveal
The team distinguishes getting through the entrance from obtaining the full experience. It hints that players may need to investigate or discover additional things in the new raids, without specifying what those steps involve.
That is not confirmation of a secret boss, a hard-mode system or a particular unlock chain. It also is not a promise that every encounter and reward can be reached without further conditions. The entrance rule answers one question; the remaining details still need an official reveal.
Developers say attunements can support storytelling and preparation, and want to use them where they make sense rather than impose one formula on every raid. The launch approach should not be stretched into a claim that future attunements are being removed.
For now, plan separate Onyxia access for the characters you actually intend to raid with. Keep the new raids' announced entrance policy separate from their still-unrevealed progression details, and wait for verified Forever-specific requirements before treating any detailed chain as a finished guide.