Rise of the Isle of the Lost
Uma was friends with Mal and Mad Maddy as a child until Mal pulled a prank on her by pretending to fall off of a dock then dumping a bucket of shrimp in her hair leaving it with a permanent disgusting stench. She watched as the VKs went to Auradon and was filled with rage and envy. She eventually befriends Harry Hook who becomes her first mate and gets her own ship. The two later recruit Gil and various others on the Isle to join their crew. She then hears from one of the goblins that King Triton's trident fell into the river on the Isle after Arabella accidentally lost it. Uma eventually finds the trident and along with her crew travels to the Isle Of the Doomed in search of a map but instead find magical items including her mother's old necklace. After a brief battle the reformed VKs retrieve the trident, leaving Uma in a fit of rage. At the end of the book she vows vengeance on Mal and the others.
After the events of the novel Uma along with Harry, Gil and her crew are attempting to break down the barrier between the Isle and Auradon. Once Mal returns after being put under too much pressure in Auradon, Ben, Evie, Jay and Carlos search for her only for Ben to be kidnapped. Uma then blackmails Mal into giving her the Fairy Godmother's wand in exchange for Ben. Towards the end of the movie she attempts to steal the wand by making Ben fall in love with her. After being confronted Uma leaps into the waters below only to reveal that she too has tentacles just like her mother, she fights Mal in her dragon form before Ben comes between them. At the end of the movie Uma emerges from the water again breaking the fourth wall to the audience hinting at another sequel.