Spike/William The Bloody
Spike, once known as William the Bloody due to his bloody awful poetry was sired by Drusilla in the 1870, the pair became lovers and, after siring and then staking his own mother, he joins Angelus and Darla and the four spend some time rampaging around Europe.  Although he mostly annoys Angelus, he does look up to him and learns from him. 

Having learnt of the existence of the slayer, Spike is determined to confront one and fulfills his wish in China in 1900 when he meets and kills his first slayer during the Boxer rebellion.

Angelus, having been cursed by gypsies and regained his soul, is the first to leave the group, at some point Spike and Dru go off on their own and Darla returns to The Master.

1977 finds Spike in New York where he finds and kills his second slayer.  The pair's travels take them to Prague where an angry mob almost kills Drusilla and leaves her weakened. 

Looking for a cure for his love, Spike returns to Sunnydale (it is not known when he was there before) where Spike tries to, but fails, to kill his third slayer.  Buffy, unfortunately, proves hard to kill and something of a bane in his life.  He also finds his old mate Angelus, who turns out to be the key to restoring his beloved Drusilla.

Life takes a turn, however, when his attempt to restore Drusilla fails to kill Angel and leaves him badly burnt and injured, now it's Drusilla's turn to look after him.  Unexpected fun turns up when Angel once again loses his soul and Angelus returns to the fold.  As Spike secretly gets stronger, Angel plans to suck the world into hell by raising the Acathla demon.

Spike, however, quite likes the world as it is and alerts the slayer to the plan.  After helping to save the world he leaves with Drusilla.  She soon gets bored of him and leaves him first for a Chaos demon and then for a fungus demon.

Spike returns to Sunnydale (interrupted only by a short trip to see his old pal Angel in LA) and teams up with Harmony who got vamped during the last apocalypse. He is soon captured by the initiative who put a chip in his head.  After escaping he finds that the chip has made him impotent, he can't hurt humans anymore.  He soon finds that he can hurt other demons though and, unwilling, ends up helping the scoobies on more than one occasion.

He soon teams up with Adam, the initiative's creation made up of various demon parts, lured by promises of a de-chipping.  Of course Adam's plans are foiled by Buffy and Spike is left with the chip in his head.

To his great disgust he finds himself falling in love with Buffy and try as he might he can't shake the feeling.  His love leads him to protecting Dawn on many an occasion and finally helping to save the world.

When Buffy is brought back from the dead, Spike finally gets his wish as they start a torrid affair, Buffy soon realises that she is using him and splits up with him.  Confused by his conflicting feelings of love for Buffy and love for evil, Buffy attempts to rape Buffy, but finds that he cannot bring himself to do it. Spike leaves Sunnydale and sets off in search of a cure, tracking down a Shaman in Africa, Spike goes through a series of trials in order to become his former self and give Buffy what she deserves.  Having completed the trials Spike receives his soul and becomes what Buffy wants, a vampire with a soul, just not the right one.

Returning to Sunnydale, Spike goes mad in the newly re-built high school basement until he is discovered and brought out of hiding by Buffy.  Meanwhile, Spike has been targeted by The First Evil who has implanted a trigger in his head which when activates, bypasses the chip and makes him kill again.  When Buffy learns of his latest killing spree she, with the help of Giles, manages to find and remove his trigger and when his chip begins to malfunction she helps him get it removed believing that now he has a soul he is no longer a danger.

Spike proves her right when the time comes and, wearing an amulet given to Angel by Wolfram & Hart and to Buffy by Angel, he finally redeems himself by giving his life to defeat The First and save the world.

The amulet has its flaws, however, and when it is recovered and sent to Angel at Wolfram & Hart, Spike finds himself resurrected but incorporeal and unable to leave Los Angeles.  He takes a little pleasure in haunting Angel for a while until the arrival of another package turns him corporeal again.  As he and Angel continue to get on each other's nerves, Angel offers Spike a job at any branch of Wolfram & Hart he may wish to go to.  When Fred dies and her body is taken over by an ancient demon, he and Angel must work together to try and save her and Spike decides that he can do more good in LA, helping Angel.  To which end he takes his part in the final battle....