Emblem of Zoamelgustar in the throne room of Zoana's royal castle.
Martina Zoana Mel Navratilova's self-declared patron, Zoamelgustar is not an actual monster. In fact, he does not even exist in real life as he is a creation of Martina's mind. Therefore, it would not be unreasonable to consider him as Martina's personal coping mechanism that consoles her during hard times as it is usually depicted in Slayers Next.
As a fabricated entity, Zoamelgustar never makes an 'appearance', although Martina usually talks to herself by mimicking what she considers to be his voice. His only physical representation in the anime consists of the talisman that is usually carried by Martina and his emblem installed in Zoana's throne room. He is also invoked in all of Martina's curses and rituals which usually bear fruit by sheer luck and not his actual intervention, as a non-existing being.
Interestingly, during episode 19 of Slayers Next, as Chaos Dragon Garv was about to strike Martina, she desperately tried to summon Zoamelgustar's protection with her talisman which seemingly worked as she was left unscathed. However, it was really just Aqualord Ragradia's power, specifically Auntie Aqua, using her talisman as a proxy.