Duclis was a friend of the royal family of Taforashia. When the Durum sickness struck the kingdom, Duclis' and Taforashia's prince, Pokota, tried to heal the residents, but the illness was too fast. Rezo, the Red Priest, appeared and put the kingdom's residents to sleep until a cure could be found. Rezo transferred the spirits of Duclis and Pokota into their current animal-like forms so they could try to find a cure without being affected by the disease.

Duclis first appears in the fifth episode of Slayers REVOLUTION. After entering the king's mansion of Taforashia, Lina and her friends are confronted by Duclis, Gioconda, and Ozel. Duclis is working for Gioconda, a marquess of Ruvinagald, who is taking control of Taforashia. Duclis' reasoning is that no one else is doing anything to save the sleeping residents of Taforashia, so he has no other choice but to join forces with Ruvinagald.

Duclis eventually turns against Gioconda after learning that she stole the aid money given by other countries to Taforashia. He activates the Zanaffar armor she is wearing, awakening a perfect Zanaffar which consumes Gioconda. Duclis makes an agreement with Zanaffar to destroy every city and country that didn't help Taforashia in exchange for making more perfect Zanaffars.

After Lina and her friends defeat Zanaffar, Duclis appears. His body is being consumed by the Zanaffar armor he has been wearing - he now walks on four legs like a centaur. He gives Pokota the opportunity to kill him, but Pokota refuses, so Duclis leaves.

(Source: Slayers wikia)