Evil Manta was mostly known for his use of spreading discord amongst others either with hypnosis or with telepathy. Either way, he could easily persuade others into doing as he wanted. Coupled with that, he has the ability to use electricity with his tail, abling to free himself from Ariel and Flounder's net.
For most of the series, Evil Manta lived up to his name, and was regarded as pure evil. He is very manipulative, even manipulating Ariel to release him from his prison in his debut. He desires power, and has wished for the trident and the Atlantican throne.
Despite his evil ways, he appears to be a good father to his son, although he does try to get Little Evil to follow in his footsteps at first. However, this also inadvertently caused him to reform.
It is known that Evil Manta was an embodiment of evil under the sea that spread discord and hatred throughout the kingdom of Atlantica, nearly causing it to implode with hatred. The ancient ones then confronted him and sealed him away, preventing him from causing any more terror in the waters.
For many years, Evil Manta was locked away under the sea and never allowed to be free. Unfortunately, he was unknowingly freed by King Triton's youngest daughter, Ariel, and her friend, Flounder. Once more, he began using his persuasiveness and charm to spread prejudice amongst Atlantica's population. However, Flounder and Ariel were unaffected; Flounder simply refused to listen, while Evil Manta had not yet come to Ariel. Together, the two were able to convince the other Atlanticans that they did not have to believe Evil Manta, and they were able to drive him away with their singing and happiness. Before leaving, Evil Manta vowed to get his revenge, and swore that he would take over Atlantica.
Not so long after, he then found a "powerful weapon" that Lobster Mobster discovered, a human's boot. (The boot had coincidentally appeared after a disaster, leading them to believe it was dangerous). Using this weapon, he threatened King Triton with the "weapon" in an attempt the throne of the king. Ariel was able to determine the boot's true purpose, and upon finding a pair of them, was able to bluff Manta into backing down.
It was later discovered that Evil Manta had a son, which he dubbed Little Evil. Though Evil Manta tried to raise Little Evil in the ways of villainy, Little Evil met up with and befriended Ariel, who introduced Little Evil to good. Unleashing a terrible force on Atlantica, it chased Ariel (and unknowingly Little Evil) around until it snapped onto Evil Manta. With Ariel and Little Evil's help, Evil Manta was rescued and presumably reformed.
Role in the series
The Evil Manta has not yet appeared yet, but he is presumedly guessed to be Ursula's superior. Scroopfan hasn't used the character yet because clips of him are not yet contained.