The true power of the Four Symbols Formation lies in its four corners, closed and self-contained, difficult to shake. The only gateway leading to the Central Palace opens outward, allowing you entry, hence Zhang Yan sought this route when entering the formation.
Upon entering the formation, he was surrounded by a dark mist on all sides, with a tunnel-like path left in the center. This represents the array's concept of "Opening Door to Welcome Guests."
Typically, when one enters the formation, it does not immediately activate; instead, it conceals its killing intent until the entrant reaches the depths of the formation, then suddenly activates.
