Even though Angor was the one who made the general frame of the illusion, there were certain elements in it that he wasn't familiar with because they were taken into existence when he wasn't himself.
The "Goddess of Sea" was also such a case. He knew he created this figure in the illusion, yet it was his subconscious that filled in the details. At first, he planned to base the goddess upon the mermaid princess. This wasn't a perfect idea because the mermaid was not an actual goddess, but only a supernatural creature who could wield a fair amount of power. But since Angor didn't know what real goddesses looked like, he followed his original plan.
However, as soon as the special mental state took control, he no longer knew what kind of entity he was forging.
