Cetus is one of Eris's pet monsters and the secondary antagonist in DreamWorks' 7th full-length animated feature film, Sinbad: Legends of the Seven Seas. He is a large Kraken-like creature who was probably based on the Kraken from Clash of the Titans. He also has yellow eyes, tentacles, a long eel-like body, a huge fish frill, and a long tail.
He was voiced by Frank Welker.
Cetus was first seen with Scorpio, Leo, Lacerta, and the Roc, as Eris demonstrated how she will make chaos to the Earth, planning it by stealing the legendary Book of Peace as she spotted it being transported to Syracuse on Proteus's noble ship, with Sinbad's pirate ship on his tail. Delighted by what fun this brought her, she sends Cetus down to the middle of the fray to attack the ships. While coming aboard Proteus's ship trying to reach for the Book, Spike bites one of his tentacles, so he flings him into the air with a piece of tentacle in his mouth before being caught by Luca.
Cetus shoots his tongue and swallows one of the Proteus's crewmen, but Sinbad sets a cannon for Cetus to swallow the cannonball as well, causing it to explode inside him and Cetus to feel nauseous, as he vomits one of the crewmen with green slime everyplace. Angered, Cetus prepares to finish Sinbad and Proteus by eating them, only to get his tongue stabbed onto the deck by a sword while Sinbad and Proteus slices off two sharp sticks from the masts and had them land on Cetus, deliberately killing him. Cetus sinks into the ocean, but not before grabbing Sinbad and taking him along to the depths.
Eris appears and puts the sinking sailor in a large air bubble, explaining that Cetus was deceased because of him. Sinbad apologizes due to the creature's attack, but after they were finished talking about Sinbad himself getting the Book of Peace for Eris, she releases him and Cetus reappears behind her, alive and well. In another scene, he was seen with the other monsters, while Eris takes a bath and she wants to see more action. She turns the ocean into ice and summoned the Roc.
When Sinbad and his crew made into Tartarus, he and Marina both got inside. While falling, all of the remaining monsters (including Cetus) watched them from above as they landed to the bottom.
Although Eris said that Cetus was deceased, it is shown that Cetus was alive and well for a stange reason. Since it is actually quite possible that he is a constellation. He is capable of turning back into a constellation at will after his job was done.