I wonder if Silas/Silvanus could be Paul's nickname for his own alter ego, the "Saul" of his prior persecuting life, his shadow side, his human side, his "sinful" side, prior to perhaps taking a "new name" of Paul after his conversion experience.
The word mystical is derived from the Greek mystikos meaning "secret," and muo meaning "concealed." Why all the mystery? Why is it concealed? Why do people keep it a secret? This seems like shady business. But is it?
Regarding the Mystery of the Gospel since the beginning.