Anon421 wrote:
Shadow suddenly appeared after he disappeared mysteriously, probably during some times after the player entered the portal with Shadow Mind.
Never mind this statement. Just realized some evidences that imply Shadow emerged from the portal much earlier than that.
Ling said at the end of Ch 4 that there are traces similar to that of Gates of Shadows at the rig on that village, and he pulled a conclusion that Shadow had returned to this world. My guess is Shadow emerged from the portal some times in Ch 2, and his return caused the series of events that led to the rig blown up. Remember a similar but tamer thing happened when we emerged from May's grave.