"A triumphant roar echoes from atop the Seat of the Aspects as Nasz'uro, the Unbound Legacy is formed."

[Ailindah-wyrmrest-accord]

Copied from another thread to give credit.

@Rainbough-moon-guard

It shows up as a Battlegrounds Neutral notification. So if you right click chat tab, go to filter settings, Other, and uncheck Battlegrounds Neutral it SHOULD stop.