SIU stands for Slave. In. Utero; it is the pen name of the author of Tower of God (신의 탑). His real name is Lee Jong Hui. He was born on 29th May, 1986.
SIU majored in Art Education in college and later undertook South Korea’s mandatory military service. There he met a sun-im (top) that also liked manhwa so he began to draw altogether manhwa. He drew any character arising out of his mind.
According to him the story "was about a guy who entered the Tower chasing a girl that was everything to him and the Tower examined the boy”. Concluding his military service, he had filled up 10 sketchbooks. The argument over those notebooks served him to create 'Tower of God'.
For more than 6 months, he had raised his work on his at Naver’s Challenge League until Naver contacted him and asked if he wanted to publish Tower of God officially. That’s how Tower of God debuted and won fame in a short time.
SIU regularly posts descriptions of random characters appearing in Tower of God in his blog and the Naver’s Cafe. The extra content acts as expansion material for Tower of God, a great story within Talse Uzer.
He regularly blogs biographies of random characters who feature in ToG or have yet to. It's all part of his extensive worldbuilding scenario: Tower of God is merely a part of his grand Talse Uzer Story. The universe of Talse Uzer is governed by a set of laws and history can never be changed. As such, there is a very finite aspect to Talse Uzer Stories.