Drusilla

Like Spike, Drusilla first appears in "School Hard" (2.3). She is perhaps one of the oddest characters in the Buffy mythology. She is also, interestingly enough, an intriguing parallel (they both have prescient dreams, and both adore Angel) and foil to Buffy herself. When Dru is first introduced, she is sickly and weak. Spike panders to her every insane whim - and she does seem to be quite insane. She speaks in nonsense phrases and observations and has tea parties with her blindfolded dolls:

"Do you like daisies? I plant them, but they always die. Everything I put in the ground withers and dies. Spike, I'm cold."
- to the Anointed One in "School Hard" (2.3).
"Miss Edith speaks out of turn. She's a bad example and will have no cakes today."
- about her favourite doll, in "School Hard".
"You know what I miss? Leeches."
- in "Halloween" (2.6)
Drusilla's prescient visions are; seen through the kaleidoscope of her madness, and yet Spike never fails to interpret them. In her first appearance, we learn some details of her past. She notes that she misses Prague, and Spike has to remind her that she was nearly killed by an "idiot mob" there. Though she spends much of her time swooning and having visions, Drusilla does manage a late night outing, during which she runs into Angel. It is here, in "Lie To Me" (2.7) that we first get an inkling of her past, Later that episode, Buffy grills Angel about the identity of Dru.
Angel: I did a lot of unconscionable things when I became a vampire. Drusilla was the worst. She was... an obsession of mine. She was pure and sweet and chaste.
Buffy: You made her a vampire.
Angel: First I made her insane. Killed everyone she loved, visited every torture on her I could devise. She eventually fled to a convent, and on the day she took her Holy Orders, I turned her into a demon.
In the two-parter "What's My Line?" (2.9 & 2.10), it is Angel's blood - because he sired Dru - and a ritual conducted by Spike that restores Drusilla to full health.
- (to Angel, as she tortures him): "Say 'Uncle'... Oh, that's right - you killed my uncle."
- "You've been a very bad daddy."
Ironically, at the end of that episode, Spike is badly injured and is left confined to a wheelchair for a long time, allowing Dru to take centre stage.

In "Innocence" (2.14), when Angel appears once more, now without a soul, Drusilla is thrilled. Not so Spike. Drusilla seems either ignorant of or pleased at the tension between the pair, and completely ignores Spike's jealous discomfort. It is implied, althogh never obviously stated, that Angel and Dru became involved again at this point. The tension continues to rise throughout subsequent episodes.

Perhaps Dru's most amusing appearance is when, affected by the love spell cast by Amy Madison in order for Xander to get back at Cordelia for dumping him on Valentine's Day in "Bewitched, Bothered and Bewildered" (2.16). In "Passion" ( 2.17), she adopts a puppy whose owner has had a small accident courtesy of her fangs.

We take another look at Drusilla's past in a flashback sequence in "Becoming, Part 1" (2.21). It is an encounter in London in the year 1860, and apparently the first time Dru met Angel. He begins to toy with her mind, the start of the horrors he would later inflict upon her. It is not until the end of that episode that we see Dru at her most evil. In that scene, she first hypnotises Kendra, the other Vampire Slayer - called at the time of Buffy's temporary death by drowning at the hands of the Master in "Prophecy Girl" (1.12) - before cutting her throat. In part 2, she also uses her hypnosis to convince Giles that she is Jenny to get him to reveal the last bit of information that Angel needs to awake the demon Acathla and destroy the world. 

But during the final battle, Drusilla is overwhelmed by Spike, who has struck up an alliance with the Slayer, and is forcibly removed from the fight. Spike and Dru then leave Sunnydale, presumably forever, but there is certainly a sense of unfinished business. She has since left Spike twice, once for a Chaos Demon and once for a Fungus Demon, saying that he wasn't evil enough for her.

Drusilla is played by Juliet Landau.