Primal Incarnates Brainrot

But only certain accounts.

Affected users can log onto alternate accounts (such as trials, etc.) just fine on the same computer; similarly, having access to multiple computers that can otherwise access WoW fine doesn't enable logging in to the affected account. So the issue is pretty solidly on Blizzard's end and not related to a specific hardware / software / addon / ISP / etc issue.

Which I think would suggest it is probably an issue tied to the character select screen, but who knows what that issue could be. A specific warband screen or combo of them? The number of characters on the account? Having last logged out on a specific player model? Having a dracthyr rogue or a night elf death knight of a specific level on their account? Who knows.

and I fully understand that this is definitely some kind of freak unpredictable bug that probably can't reliably be produced on the PTR, because like, it's definitely going to turn out to be some completely bizarre interaction between different elements of code. But it's still pretty annoying that their only acknowledgment of such a major bug affecting hundreds (if not thousands) of players is a single reply from the CS twitter that they're "looking into it" & not even putting it on their known issues list (probably because of the colossal memory leak associated with the bug)