Merlumina was a member of the Tribe of Ancients. Her name is a portmanteau of "Merlon" (or his namesake himself, Merlin) and "luminous". 1,500 years before the setting of Super Paper Mario (the only game she appeared in), she was told to protect the Pure Heart in Yold Ruins and await the hero of legend. 1,500 years later, her ghost still waited (albeit slightly impatiently) for the hero to arrive.
Unlike most of the "Shaman"-type characters, details about Merlumina's childhood are known. According to her, in her youth she was quite attractive. It was hard for her to get to sleep, though, so her mother would sing her a lullaby. When she stopped living with her mother, she needed four men (all of whom were in love with her) to sing her lullabies. Merlumina was quite a mischievous girl, and would seduce men in their dreams. To make her sleep for 1,500 years (so she could successfully complete her mission of giving the destined hero, later proved to be Mario, the Pure Heart she guarded), Merlumina needed the entire village to sing a lullaby for her.
Super Paper Mario
After Mario defeated Fracktail, a door appeared. The door brought him to Merlumina's chamber. Following the Paper Mario series tradition of "Shaman"-type characters having extremely long and boring stories, Merlumina told Mario the "short" version of her history. By the time she was done, Mario was fast asleep. Also, like most similar instances in the earlier Paper Mario games, Merlumina did not notice that Mario and Tippi had fallen asleep (and Mario denied that he did anyway). After the story, Merlumina gave Mario his second Pure Heart, ending Chapter 1.
Later on in Super Paper Mario, a chain of optional requests wound up with Old Man Watchitt requesting that Mario and friends remove the spirit haunting his dreams (and get the spirit's autograph). The spirit was indeed Merlumina, and Mario and co. returned to find her. It turned out that Merlumina had attempted to take a short nap after handing over the Pure Heart, but she couldn't fall asleep. Worrying that she had become a forgotten phantom, she tried counting sheep. Even after counting the 100,000th sheep, she still could not fall asleep, so she decided to take her frustration out on somebody else by haunting somebody in Yold Town. This somebody happened to be Watchitt, who was distantly related to her (being another descendant of the Tribe of Ancients) and therefore be able to hear and respond to her haunting. It didn't help her much with her insomnia, however. When Mario and co. came looking for her, Merlumina told them another long story about her childhood (and how she'd haunt people she loved), and again Mario fell asleep but denied ever doing so. After conversing some more about Watchitt, Merlumina told another long story. In the end, though, Merlumina wrote an autograph for Watchitt (allowing Mario and co. to retrieve the You-Know-What from Watchitt and eventually earn Piccolo), after which point she finally falls fast asleep.
After the player gets Merlumina’s autograph, if they use Tippi to tattle the place where Merlumina just disappeared, Tippi will only say: "........." If the player flips, they can still see her shadow on the floor, but if they leave and re-enter the room, the shadow vanished as well, and Tippi can’t say her tattle anymore.
According to Garson in the Flipside Bar, Merlumina had a younger sister. She was entrusted with the violet Pure Heart to deliver to King Sammer I, but they fell in love and got married, eventually having 100 children.
Merlumina is one of the two ancestors of Merlon who is a spirit, the other being Madam Merlar.
Names in other languages