He was captured by the U-TIC Organization during the mine workers' riots. He was subsequently held as a connection experiment test subject at Labyrinthos. He was experimented on with drugs for six months - although his link affinity to Realians were high compared to other test subjects, abnormalities in the pulses of the frontal lobe and the tectum appeared during a connection experiment, which resulted in his death, accidentally. It is believed he was unable to resist the fear against U-DO.
While his father Aizen Magus is convinced that the U-TIC Organization murdered Tethlla during the riots, Tethlla's daughter Mai Magus still believes somewhere in her heart that her father is still alive. Aizen comments that Mai believes her father's "soul" lives on in Leupold.