Darla

Darla is introduced in "Welcome to the Hellmouth", the first episode of Buffy the Vampire Slayer, in 1997. It is revealed early on that she is a vampire, initially in league with the Master, Buffy Summers' primary antagonist in the first season. Darla's backstory is disclosed in the episode "Angel", where it is revealed that she is Angel's sire (the one who turned him into a vampire) and former longtime lover.

The character appeared in numerous flashback episodes, until she received a significantly expanded role in Angel. Darla has died a total of four times, making her the character to die the most often in the two series. In Angel, she is resurrected by the evil law firm Wolfram & Hart in an attempt to weaken Angel. She later became intertwined in many of the story arcs in the second and third season. Darla becomes pregnant, a unique occurrence for a vampire. She sacrifices herself in order to give birth to her and Angel's human son Connor, ending her run on the series. However, Benz continued to appear in flashback episodes during the next two seasons.

Drusilla

Drusilla is introduced alongside her lover Spike (James Marsters) in the second season of Buffy the Vampire Slayer to serve as new antagonists to the series' heroine, vampire slayer Buffy Summers. In contrast to the series' previous central villain, the ancient and ceremonious Master, Spike and Dru were introduced as more unconventional but equally dangerous pair of vampires. Though Spike and Dru had not been conceived as necessarily having to be either British or American, Landau chose to portray Drusilla with a Cockney accent in keeping with the characters' "Sid and Nancy analogy".

The character's backstory gives her ties to Buffy's boyfriend Angel, and it is gradually established over the course of Buffy and Angel. A young psychic in Victorian London with a potential for sainthood, Drusilla was driven insane by Angel before he eventually turned her into a vampire. In Angel, the character recurs both in the present-day narrative and in flashbacks which depict the title character's adventures across Europe and Asia with Drusilla and Spike.

After Angel ended in 2005, the character continued to appear in Expanded Universe materials in other media. Landau went on to co-write a two-issue Drusilla story arc for IDW Publishing's Angel comic book series in 2009, continuing her character's storyline.