Merchieftainess Murcus is the leader of the Merpeople colony residing in the Great Lake on the grounds of Hogwarts School of Witchcraft and Wizardry. She is a key figure during the second task of the 1994 Triwizard Tournament. While initially appearing as an obstacle to Harry Potter, her strict adherence to rules and her subsequent honest testimony to Albus Dumbledore prove crucial in acknowledging Harry's “moral fibre” and awarding him a high score.
Murcus's history is largely unknown, with her only recorded appearance occurring during the 1994-1995 school year. As the Merchieftainess, she held authority over the Mer-village in the Great Lake. Prior to the second task of the Triwizard Tournament, Albus Dumbledore, a known speaker of Mermish, negotiated with Murcus. She agreed to have her people guard four “hostages” — Ron Weasley, Hermione Granger, Cho Chang, and Gabrielle Delacour — in their underwater village for the champions to rescue. On 24 February 1995, during the task, Harry Potter was the first champion to reach the village. He successfully freed his own hostage, Ron Weasley. When he attempted to free the others as well, Murcus and her armed guards confronted him. She gestured forcefully that he was only permitted to take his own hostage. When Harry drew his wand, the Merpeople surrounded him, shaking their spears threateningly. Despite their intimidation, Harry refused to leave the other hostages behind. After the time limit for the task expired, Murcus's people allowed Harry to ascend with both Ron and Gabrielle Delacour, as Fleur Delacour had not arrived to rescue her sister. Following the task, Murcus provided a detailed and truthful account of the events to Albus Dumbledore. She explained that Harry had reached the hostages first but had remained behind out of a noble desire to save everyone, even at the cost of his own standing in the tournament. This report led the judges to award Harry second-place marks for his display of outstanding moral character, tying him for first place overall with Cedric Diggory.
Merchieftainess Murcus is described as having wild, dark green hair, a yellowish face, and matching yellow eyes. Her teeth are also yellow and broken. She wears a necklace that appears to be made of shark teeth. As a leader, Murcus is stern, authoritative, and a strict enforcer of agreements. She is not intimidated by a wizard, even one pointing a wand at her, and she commands her people with clear, non-verbal gestures. Her primary loyalty is to the terms of her arrangement with Dumbledore. However, she is also possessed of a strong sense of justice, as demonstrated by her fair and honest report of Harry Potter's actions. She may seem fierce, but her actions are guided by principle rather than malice.