1. Ellen Scott: For Ellen, you've already provided a detailed description of her physical appearance and personality traits. You can further develop her character by exploring her motivations, backstory, and how she interacts with other characters in the story. Consider delving into her fears, desires, and the events that shaped her cautious nature.

2. Jack Brown: Similar to Ellen, you've described Jack's physical appearance and personality traits. To add depth to his character, contemplate his background, experiences, and how his loyalty and humor play into the dynamics of his friendship with Ellen. You could also explore how his perceptive nature helps him understand and support others.

3. Alexander Stone: Utilize the captivating physical features you've described to enhance Alexander's character. Consider showcasing his calculative and manipulative nature through his actions and interactions with other characters. By delving into his motivations and backstory, you can create a complex antagonist that challenges Ellen's goals.

4. Samantha Davis: You've already established Samantha as a rival to Ellen, but you can further develop her character by exploring the reasons behind her resentment and her relentless desire to undermine Ellen. Consider adding layers to her personality, such as vulnerabilities or hidden insecurities, which can make her more three-dimensional.

5. Marcus James: Marcus is portrayed as a reliable and helpful colleague, but you can expand his character by exploring how he deals with office politics and the strain it puts on his friendship with Ellen. Delve into his personal experiences and conflicts, as well as any growth or development he experiences throughout the story.

6. Rebecca Thompson: Rebecca is presented as a mentor figure, so reflect on her past experiences and wisdom gained over the years. Consider how she provides guidance and advice to Ellen, and explore her own personal struggles or challenges that she has faced throughout her career.

7. Stephanie Turner: Highlight Stephanie's intuitive and supportive nature, and depict how she provides emotional support to Ellen and Jack. Explore her friendship dynamics, past experiences, and consider incorporating her perspective on the conflicts and challenges the other characters face.

8. William "Will" Hayes: Although brief, you've provided some details about Will's physical appearance and loyalty to Alexander. Consider delving into his backstory, exploring his motivations, and adding complexity to his character. Showcase his loyalty in different situations and reveal sides of him that are unexpected or contradictory.