Magus Lock
The Magus Lock wasn't a technique, it was rather a magnum opus, a life's work a "Magus" could and would spend their entire lives perfecting.
The Magus Lock was essentially a permanent Visualization built within one's Spiritual Sea, a lot like Ryu was already used to. And, much like the [Divine Chaotic Annihilation] Visualization of the past that used to perpetually protect Ryu's mind, so too would the Magus Lock, but via a much more profound method.
While [Divine Chaotic Annihilation] relied entirely on brute force and the use of an esoteric law, the Magus Lock, while it too could rely on brute force sometimes, could also make use of softer methods and other forms of subterfuge.
The Magus Lock was precisely that, a lock placed on the mind that made it difficult to access the core of one's soul.