An inventor of the Rosenkreuz Orden, Isaak is also called Panzer Magier. Isaak is the vampire who is responsible for making Cain's current body, which had been permanently damaged by Seth and Abel 900 years ago. Despite his many talents, Isaak is somewhat of a mystery and has gone by many aliases in the past. He used to study at London University under the name of Isaac Butler, and was involved in the incident which killed William's fiancé and led to both to them being expelled. Since he met Cain, Isaak takes care of Cain's regeneration and leads the Orden with him, though his true motivation for doing so is unknown. He enjoys smoking cigarillos and quoting works of literature. Issak does not usually appear in public, preferring to let others carry out his plans. When he does move to the front lines, he shows excellent battle prowess and is not easily defeated.

Isaak possesses many talents and is well versed in the use of Lost Technologies. His primary weapon is an attack called the Arrow of Belial, a massive sphere of light that shoots a multitude of energy bolts at his opponent. He also possesses the ability to project a nearly impenatrable electromagnetic wall, known as the Shield of Asmoday, around his body. This defense can be utilized at will and is capable of blocking almost any assault. In addition, Isaak created artificial demons that he can summon into battle to aid him. He has two kinds of demons: dwarfs called the "Schatten Kobolds" that appear to be little devils concealing their forms in Kämpfer's shadow, and knomes, monstrous worm-like creatures with the ability to tunnel through the ground at amazing speeds. The latter only appear in the novels. His hair, which is made of thin mono-carbon fibers, is strong enough to cut through the hardest diamond making it another formidable weapon.

According to the novels, Dietrich von Lohengrin is Isaak's protege and it is probably under his tutelage that Dietrich gained the knowledge to create the Death Hunters. Isaak is last seen piloting the Orden's air ship while leading an attack on the city of Londinium in Albion. Through the combined efforts of the Church and the Kingdom of Albion, the ship was destroyed, presumably killing him in the explosion