While most of the original footage was lost, a VHS workprint has been discovered that carries a lot of the footage, including much of Blatty’s vision for the film. Shout Factory’s release boasts the original title, Legion, as well as a new assembly of the film that includes said shots from the discovered VHS. So while it’s not 100% Blatty’s original vision, it’s allegedly close.
What’s so interesting about juxtaposing the two cuts is knowing that Legion is Blatty’s direct sequel to The Exorcist. Legion feels intimately connected to the 1973 classic, while the theatrical cut is an action-packed quasi-sequel that forces connections to William Friedkin’s adaptation.