Occupation of Heimdallr
Zoro-Agruga occupied Heimdallr from S.371 to ca. S.470 and, with the dark breath it sprayed, turned the capital into the city of the dead. Zoro-Agruga's reign ended with the counter-attack of the Imperial family, led by Emperor Hector I, wielding the Vermillion Divine Knight Testa-Rossa. Upon its death, its blood claimed Hector's life and placed a curse on the Divine Knight.
Its remains were locked away below the newly built Heimdallr.
Reanimation through artifact
In S.1204, Zoro-Agruga's carcass was brought back to life by Michael Gideon of the Imperial Liberation Front, through the means of an artifact shaped like a flute, referred to as the Demonic Flute. Class VII managed to hold off Zoro-Agruga until Gideon's flute was destroyed and the dragon's remains returned to their eternal slumber once again.
The Dark Dragon's Revival
Zoro-Agruga is encountered and fought in his sanctuary, the gateway to his plane which appears underneath the Imperial Museum. With the assistance of Roselia he is defeated. She describes the dragon as being the greatest Cryptid.