I loved this movie but I did notice something strange. The Butterfield in the opening scene was not the same Butterfield as in the rest of the movie. As it happens there were two seperate actors that played young and then older Butterfield. This is one of the most pointless things that I have ever seen. Both actors are only seperated by 7 years in age and the younger Butterfield could have easily played his older counterpart, or vice versa. Why pay two actors to play the same part when they could've just paid one to do the whole thing? Silly.
When Nix was "killed", Butterfield was left with the task of learning enough magick to free him and resurrect him. He went into hiding, and because of the (implied) crimes he and Nix committed as members of Nix's cult, when he needed to move around in the world he had to change his appearance in order to avoid being caught by the law (kidnapping charges, at the very least), or by Swann's group (who probably eventually believed he was dead). Essentially, if Swann had found him Butterfield would not have been able to ever free Nix, as Swann would have been more powerful at the time, and would have blocked Butterfield (or killed him).
Butterfield changed his appearance through magickal means; An illusion that made him look different, so that he could slip through the cracks and study for years to become a skilled enough magician to perform the ceremonies necessary for his master's return.
The Butterfield in the beginning of the movie was the true face of Butterfield. The one you saw later was him almost two decades later, cloaked in illusion and ready to do some major dark magick.
The older Butterfield who was "cloaked in illusion" still had white eyebrows, one brown eye, and one blue eye, like his younger, true face. Care to explain that?