In his book The Art & Craft of Playwriting, Jeffrey Hatcher says, ” When you’re sure you have an interesting character, your next step is depicting this character to your audience. ‘Action is Character,’ goes the old saying, ‘as character is action.’ They cannot be separated” (27).
What he’s saying is that what a character says (the lines that you write for him) is not as telling as what a character does. A character in a play may tell his wife that he loves her more than anything in the world, but if we see him seducing his secretary in the very next scene, his actions suggest that he’s a womanizer. As Batman says in Batman Begins, “It’s not who I am underneath, but what I do that defines me.”
One of the best examples of Hatcher’s point is the character of Sauron from The Lord of the Rings. As far as villains go, the only direct characterization of Sauron is a giant, lidless eye. He does not directly interact with or speak to anyone as a character, and essentially, he’s fairly absent from the plot all together. How do we know that he is the villain? Because of what he does throughout the story. The part of him that dwells in the ring corrupts and ruins anyone it ensnares, and we see how heavy a burden the ring is on Frodo as he tries to destroy it. He uses ring wraiths, orcs, the wizard Saruman, and the army of Uruk-Hai to fight for him as he seeks to subjugate Middle Earth. Through the sheer force of his will, he commands his armies, enslaves men, ruins cities, and seeks to regain his ring so that he can come to power again. All without uttering any lines of dialogue.
When you are crafting the plot of your play, remember that the way you develop a character has more to do with the actions they perform than the lines they say. The fundamental parts of who they are lie in the general qualities and personality traits you give them, but who your characters really are is connected to how they respond to and overcome conflict, how they interact with other characters, and how they go about getting their wants and needs met.