Joachim Guenter was born in S.1170.
He studied at the Medical University in Remiferia. He ultimately moved to Crossbell to start working at the St. Ursula Medical College as an associate professor. All this time he stayed in touch with his former classmate, Professor Seiland, by sending her regular letters.
An associate professor by day, Joachim served as one of the last, if not only remaining, high priest of the D∴G Cult, which denies the existence of Aidios. By taking Gnosis, Joachim was capable to work as a professor during the day and fulfilling his duties as a high priest at night. The drugs also turned his hair from the original grey colour to light blue.
During the Cult Incident in Crossbell, it is revealed that many of the strange occurrences in the state were (in)directly caused and manipulated by Joachim. He was Ernest Reis's physician and prescribed him Gnosis, which led to Ernest's abnormal obsession with the mayoral position of Crossbell to the extent of an assassination attempt on Mayor Henry MacDowell.
It is also revealed that he handed Gnosis to the Boss of Revache, Marconi, who in turn handed this to Preston, then-commander of the Crossbell Guardian Force, in the form of a 'supplementary nutrition'. Indirectly, this gave Joachim control over thousands of troops.
When he was finally corned by a collaboration between the Special Support Section and Bracer Guild, he was labelled as "more heretic than Red Constellation" by Randy Orlando, "no longer human" by Elie MacDowell and "even more disturbed than Weissmann" by Joshua Bright.
Before the battle, Joachim's blue hair colour returned to its original grey. His weapon of choice is a magic wand, that grants him control over the three higher elements. He even mimics the Evil Eye that Georg Weissmann used, based on the memories of Estelle Bright he was able to perceive through the Gnosis.
When Joachim realises he has been driven into a corner, he takes an overdose of Red Gnosis and transforms into a demon. At the height of the battle, he extends his demonic arms and thrusts them through the floor toward the S.S.S and bracers, capturing them for a final attack. He is stopped, however, by Renne Hayworth and Pater-Mater. Once the others are freed, they erase Joachim from existence.