Abarekiller 
basically, from Scott's post on the matter
The book itself is non-canon, but elements from it are.
The elements we know is canon is
William Afton
A "creator" of the animatronics being killed by a nameless animatronic after depression.
What we don't know if is Afton is "Purple guy" which again, in my theory, he isn't Ennard is (know matter how you look at it, that ending gives you "Purple Guy origins" feeling)
which from there, we could figure out.
Afton killed by Ennard, Ennard takes on Afton's appearance
Ennard kills the other "Creator" in "FNAF World" Secret ending, and (under Baby's voice) says "The show will begin" probably a sign of the killings as "The Purple Guy"
keep in mind, the "other creator" has to be killed after sister location, since none of the animatronics had left.
The major question is now. Who the fuck is Balora?
The book itself is non-canon, but elements from it are.
The elements we know is canon is
William Afton
A "creator" of the animatronics being killed by a nameless animatronic after depression.
What we don't know if is Afton is "Purple guy" which again, in my theory, he isn't Ennard is (
which from there, we could figure out.
Afton killed by Ennard, Ennard takes on Afton's appearance
Ennard kills the other "Creator" in "FNAF World" Secret ending, and (under Baby's voice) says "The show will begin" probably a sign of the killings as "The Purple Guy"
keep in mind, the "other creator" has to be killed after sister location, since none of the animatronics had left.
The major question is now. Who the fuck is Balora?