Reference:
Jung, E. and Von Franz, M. L. (1970) The Grail Legend. English Translation, Princeton University Press, Princeton NJ

p88-89. “…the latter (the sword) symbolizes not only the separating and discriminating aspects of the intellect, but also the judging, wrathful intervention of God in earthly affairs. …
The sword signifies that life-urge which leads to the recognition of the Self.”

p91. “It seems then that the Grail King has been “struck” by an impulse rising unexpectedly from the unconscious with which he is unable to come to terms. This impulse emerges from the heathen layer of the soul or else from a dark opponent behind whom God Himself appears to be standing.⁴⁴ The suffering of the King will endure as long as this unconscious impulse is not realised in consciousness.”