In the recent Buffy episode “Villians”, black-magic & vengeance crazed Willow uttered the words “Bored now” just before she flayed Warren. This was an obvious shout-out to Vampire Willow using the phrase in “Dopplegangland” in season 3. Anyway, I was wondering, is there a term in English or in drama for a line or other utterance that the speaker uses to announce his or her intent of impending doom, mayhem, etc.? The only other good example I can think of is Jules’ speech from Ezekiel in “Pulp Fiction”.
A threat?
No, something more specific, like a catch-phrase, except it is only used in this particular situation. Jules said that he always recited that Ezekiel speech to whoever he was about to kill.
Calling card?
That’s the best I can do.
How about malediction, which is:
…A denunciation invoking a wish or threat of evil or injury
“Catchphrase” would cover it. That’s for any line associated with a character; I don’t think there’s a separate word meaning “evil catchphrase.”
This would have been my guess too.
I just noticed the irony of “Osiris” posting to a Willow-related thread… 
I looked up “death knell”, or rather “knell”, since my dictionary apparently considered the death part redundant, and it seemed to match, but it just sounds too vague, almost a synonym for “swan song”. If we have a word like “battle-cry” to describe what is said just as the fight begins, there ought to be one for what is said just as the fatal blow strikes. While we’re at it, after watching that last scene of “Villians” I also wonder if there is a word for incinerating someone or something so quickly and completely that they are vaporized, not even leaving ashes.
This is all Bill Bryson’s fault. After reading “The Mother Tongue” and “Made in America”, I’m convinced that the English language has a word for everything, even if we have to steal it from another language, like that German word for taking joy in the misfortune of others. 
How about “signature”?
Character Line?
Schadenfreude, pronounced “SHAW-d’n-Froy-duh.” A most useful word, indeed.
What about “foreshadowing”?