Seahorse demon mythology:

Kunopegos ("dog-flow" or "cruel sea-horse demon") is a demon in the shape of a sea horse. Kunopegos is a cruel spirit who raises himself up like great waves in the open seas, causes seasickness among sailors, and sinks ships in order to claim the bodies of men and their treasures. He consults the prince of demons, Beelzebub. He can go to shore as waves and shape shift into the form of a man. He is thwarted by the angel Iameth.

In the Testament of Solomon, Kunopegos tells King Solomon that he can shape shift into a man. Solomon confines Kunopegos by casting him into a broad flat bowl filled with 10 receptacles of seawater. The top is fortified with marble and the bowl’s mouth is covered with asphalt, pitch, and hemp rope. The vessel is sealed and stored in the Temple of Jerusalem.

Toxic Seadragon backstory:

This breed of what is believed to be like the Kunopegos is a toxic version of the sea storm bringing monster.

He ravages people's homes and lives and takes women as his personal slaves up until they are no longer useful for him.

He has a very poisonous touch, earning him his name, and can control how much or little poison he can unleash on his victims.

Here's an older version of Toxic Seadragon. What do you think of this evil sea demon?