Friendship Birb
Friendship Birb was the community initiative where players group up to help others take down Argus the Unmaker in order to obtain the Violet Spellwing. Multiple organizers were putting together groups of geared and experienced individuals to help those in need of the mount at absolutely no cost to them. Violet Spellwing is no longer obtainable therefore the event is now over.
The new end-of-expansion raid mount for Battle for Azeroth is the Uncorrupted Voidwing and you can get it by defeating Heroic N'Zoth in Ny'alotha.
If you don't have a guild or friends to help you kill N'Zoth, then consider joining Wings of Azeroth, the same community that helped over 2000 players get their Violet Spellwing for free! Check their #announcements channel for more info or follow their channel on discord to stay up to date on when runs start.