"I'm going to rip her spine out of her body, then I'm going to eat her heart and suck the marrow from her bones." ~ Kakistos
Kakistos was an ancient vampire who had lived so long that he had developed animal-like traits and a vicious personality to boot: he was the main antagonist of the Buffy the Vampire Slayer episode "Faith, Hope & Trick".
History
Antiquity
Already old in the time of Greek antiquity, Kakistos had unusually cruel habits regarding his prey. Rather than killing, or even turning all of his victims, he would often torture female prisoners, driving them mad until they became his servants. These mad women became known as the maenads.
At some point, the maenads raided the village where Artemia, the Slayer, lived. Although she was away at the time, both Artemia's husband and daughter, Alexandra, were present during the attack. Her husband was killed in the battle, but Alexandra remained hidden.
On the Father's orders, both Artemia and Alexandra were captured and tormented. Alexandra's mind was broken, and she made a deal with D'Hoffryn to become a vengeance demon. She then used her powers to destroy the maenads, and was about to grant Artemia her dying wish to destroy the Father when a battle in Arashmahaar erupted, robbing Malice of her powers. The traces of this wish would remain dormant for thousands of years.
20th Century
At some point in time, Kakistos became the leader of the Cult of Antemorh. This vampire cult was thought to have been destroyed prior to World War I. Geoffrey Wyndam-Pryce's father had died trying to destroying the cult and its leader. During World War I, Kakistos resurfaced and offered his services to Kaiser Wilhelm II. He reformed his cult, gaining Crixus as his main lieutenant. Along with regular ground assaults on allied troops, Crixus had his vampires drop on enemy forces from planes and zephyrs and feed on or turn them. However, the vampires also attacked German forces occasionally. After each attack, the vampires would leave behind a symbol of their cult, painted with the victims' blood. Geoffrey Wyndam-Pryce, set out to finish what his father started. In France, Wyndam-Pryce formed an uneasy alliance with Angel, and together they ended Kakistos's involvement in the war.
By 1940, Kakistos had moved to the Louisiana bayou, where he established a base. There, he granted Spike and Drusilla permission to hunt down a potential Slayer.
Sunnydale
Years later, Kakistos was stationed somewhere around the East coast of America, possibly Boston. There, he confronted Slayer Faith Lehane, kidnapping her Watcher, Diana Dormer. After luring Faith to his lair, Kakistos ripped Dormer in two, and promptly captured Faith. Faith, however, was not as helpless as she seemed. With the aid of Artemia's spirit, she was able to land upon the Father both a sword slash to the groin and an ax wound that cleaved his face in two, a wound from which he would never fully recover. Faith was then able to set the support beams of his lair on fire, brining to entire structure crashing to the ground.
Kakistos traveled to Sunnydale to hunt down Faith. With him came an entourage of his minions, most of them fanatical followers led by Mr. Trick, Kakistos' right hand and a technophile, modern-minded vampire, who abandoned his master to be slain by Faith and Buffy Summers. Kakistos was finally slain by Faith who overcame her fear of him and impaled a two by four through his chest, staking and killing him.