In Children of the Corn (1984) a child named Isaac was said to be the first who led the children into killing people and their parents to sacrifice them to He Who Walks Behind The Rows. Isaac leads the children and told them once all adults were gone, they would find a truth.
Like many unseen and powerful demons, "He Who Walks Behind the Rows" could be another name for Satan or it could be a completely separate entity - other antagonists in Stephen King's work also had rather abstract forms, the true form of Pennywise for example was said to be an almost Lovecraftian super-entity. "He Who Walks Behind the Rows" is demonic version of the Old Testament God and his appearance is shown in strange mosaic of a pagan Jesus stuffed with corn husks and leaves. In the SyFy version of the movie, He is called the "God of the Old Testament".
It is implied that He Who Walks Behind The Rows is none other than Randall Flagg.