- It provides a contrast to the main plot of Lear and his daughters. Lear's daughters are selfish and power-hungry, while Gloucester's son, Edmund, is even more so. Edmund is willing to betray his own father in order to gain power. This contrast highlights the difference between true and false love, and shows how easily people can be misled by appearances.
- The subplot illustrates the themes of chaos and order in the play. Edmund's actions cause chaos and disruption, not only in his own family but in the kingdom as a whole. This disorder is mirrored in the natural world, which is also plagued by storms and violence. The subplot suggests that there is a deep connection between the inner world of human emotions and the outer world of nature, and that when the one is disturbed, so is the other.
- The subplot contributes to the play's tragic ending. Edmund's betrayal leads to Gloucester's downfall, and ultimately to his own. It also alienates Regan from her father, and this alienation plays a role in Lear's tragic madness. The subplot thus shows how the actions of one person can have far-reaching consequences, and it underscores the tragic futility of human ambition and power.
In short, the subplot in King Lear is important because it provides contrast to the main plot, illustrates the themes of chaos and order, and contributes to the tragic ending of the play.