Kemmler is considered to be one of the most powerful warlocks and necromancers of all time. He practiced what he called 'true magic' in which magic is used to control life and death. His main focus was necromancy, for which he was renowned. He was deemed such a risk that the entire White Council hunted him down in 1961.
He had power over the dead and demons, pals with most of the Vampire courts, every "nasty" in Europe, and some of the scarier Faeries. He had his own cadre of apprentices and thugs: "Baby Kemmlers", who followed him in his footsteps and practiced the darker arts.
Kemmler had learned a way to bind his will to shades, not just the dead, to devour them in order to feed his own power. It was what allowed him to defy the entire White Council for so long. This secret of using ancient spirits in this way for the Darkhallow is written in The Word of Kemmler.
Kemmler's power was so great that, in 1961, it took the entire White Council: the Merlin the Senior Council, the Wardens, and the "brute squad" out of Archangel, plus every wizards and ally that they could find in order to destroy him. They had killed him several times. After the time the White Council killed him in the early ninteenth century, they chose not to take any chances.
He was responsible for WWI, the whole thing. There was about 150 years of history behind it and Kemmler had his hand in several facets of it. He vanished after WWI then reappeared in WWII when he animated mass graves and rampaged through Eastern Europe. It's uncertain how many he actually killed.
In the series Edit
- Main article: Ghost Story
- Main article: Cold Days
In Cold Days, Harry learns from Bob that Halloween night is the only time that the Darkhallow could turn a wizard into an Immortal since. This is because Halloween Night is the only time of the year when the "locked stasis of immortality becomes malleable"—they can add new power to their mantles of immortality by feeding: taking in new energy. He also learn that Halloween is the only time they are vulnerable to being killed.
The Heirs of Kemmler Edit
- Main article: Heirs of Kemmler
The Heirs of Kemmler intend to call up ancients spirits using the Erlking and then devour them for power on Halloween Night during the powerful Darkhallow spell that will turn one of them into a god-like being with ungodly powers.
- Main article: Darkhallow
Evil Bob: The Word of Kemmler contains: "Knowledge. Truth. Power. The master wrote down his teachings, wizard, so that those who came after him could learn from him. Could learn about the true power of Magic. What you call magic is nothing more than parlor ticks beside the power to master life and death itself." 
- Kemmler is possibly named after the master necromancer of the same name from the Warhammer fantasy table top game.
- Kemmler may also be partially based on William Kemmler- who on August 6th, 1890, was the first man executed through the use of the electric chair.
- Perhaps Kemmler is named after Heinrich Himmler, the head of the Hitler's S.S., given the tendency in Anglicized pronunciation to say "Heinrick Hemmler" which sounds similar to "Heinrich Kemmler".
In Cold Days, Harry learns that it is only on Halloween night the Darkhallow ritual can turn a wizard into an Immortal. Halloween night is when the locked status of immortality becomes malleable and an Immortal can add power to his mantle by feeding on energy. Given that Kemmler was killed carefully on Halloween (ref?) night in 1961, it is possible that he became an Immortal on Halloween long before he attempetd the Darkhallow. This could explain why it is mentioned in Ghost Story, that the White Council killed Kemmler seven times before it became permanent—the last and final one being on Halloween night in 1961 which happens the only night of the year that Immortals can be truly killed. 
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 Dead Beat, ch. 3
- ↑ 2.0 2.1 2.2 Dead Beat, ch. 21
- ↑ 3.0 3.1 Ghost Story, ch. 17
- ↑ Ghost Story, ch. 44
- ↑ Ghost Story, ch. 28
- ↑ 6.0 6.1 Cold Days, ch. 11