Velenka is a devious mako from the Shark Wars book series. Although she desperately wants to be the Big Bad of the series, she is constantly outmaneuvered by stronger power players.
Originally the 5th in line of Goblin Shiver ("Shiver" meaning "shark clan"), Velenka came across Gray, a megalodon pup, and attempted to sway him to her way of thinking. She attempted to overthrow Goblin by using the heroic megalodon, but this plan failed when Takiza, the fighting fish and master of Shar-Kata, conjured a whirlpool, sucking her and her fellow Shiver members into it before throwing them into the mighty current.
Everyone survived, however, and Velenka eventually had Goblin assassinated by poisonous dwellers. Taking control of the Shiver and renaming it Riptide, she allows her Shiver to be conquered by Finnivus, the tiger shark king of Indi Shiver. Finnivus takes an interest in her. As Finnivus becomes emperor of the seas, Velenka decides to secretly poison him and eventually put herself on the throne to give herself a shot at ruling the ocean. This fails when Finnivus and his court shark put a stop to it. To prove her loyalty, she is force-fed poison by the cruel young emperor and slowly weakens. She must swim with the emperor on the front lines in war to further prove herself. Finnivus and Gray have a showdown, with Gray mortally injuring him by biting off his tail.
Velenka attempts to flee, but is rammed by Mari and captured. She attempts to suck up to Gray for forgiveness, but is left in her cage until the main antagonist, Hokuu, breaks her out and uses her as his pawn. Upon revealing he will guide the antagonistic ruler of Fifth Shiver, Drinnok, into the Big Blue from the under waters, Hokuu tells Velenka she'll be the last to die, and that it'll be a complete honor.
Horrified by Hokuu's evil, Velenka flees and joins up with the newly-reformed Riptide, led by Gray's friend Striiker the great white. She realizes her evils and desperately asks for redemption after Barkley saves her life from another frill shark.
She joins the war against Grimkahn the mosasaur and Hokuu (who betrayed and fatally blasted Drinnok), and Gray ends the battle by destroying Grimkahn from the inside. Hokuu later devastates Gray in a final battle before being vaporized by Takiza, though not before mortally injuring him.
Barkley promotes Velenka to being his advisor after being named a new leader by Gray, completely redeeming her and establishing his trust in her.