When Shang Tsung returned to Earthrealm to once again attempt to conquer it via Mortal Kombat he brought with him Goro, who is said to have once been Tsung's pupil. I've often wondered in what capacity the Shokan Prince served as Tsung's pupil.
Consider this. At the time of MK1 Goro was 2,000 years old. He had reigned as champion for about 500 years and before that Tsung had controlled the Tournament for an unspecified period of time (check out this article for more on that). This means Goro was somewhere in the neighborhood of 500 years old and, though we don't know much about a Shokan's life expectancy, we can pretty safely assume he'd have been physically grown, though possibly not fully mature mentally - much like a human teenager. As such, Goro would have been well versed in hand-to-hand kombat, brutality, fearlessness, and the like by virtue of his people's culture. Also, he may have had some inherent knowledge of magic as evidenced by the Shokan's curse on the Centaurians in MKA. So what, if not fighting or magic, did Shang Tsung teach Goro?
My guess is that Goro's training under Tsung was meant to bolster these already formidable traits. Tsung probably refined his brutal nature and taught him strategy not just as a fighter but as a military tactician. Tsung most likely honed Goro's skills and groomed him for life as an elite appointed official under Kahn. Tsung was an ideal choice for this because he not only served Kahn in a similar capacity (as Chief of the Shadow Priests) but because Tsung would be one of a very few Outworlders who both had poise and grace and also the ability to command the Shokan Prince's respect as a warrior.