Linn Regiostar

Linn Regiostar (リィン・レジオスター) is the father of the Church of Alexander Mark who died and became a ghost. He is apparently a RPG and dungeon crawler fanatic as he became a spirit because he died from a poison arrow trap in a dungeon he built underneath the church using all the church's donations. At first he was spiritually bound to the dungeon, but after it was destroyed, he appears in the outside world and now moved to Nagi's mansion, where he follows and haunts Hayate. Unfortunately for Hayate, only people who have been in the dungeon before can see him. Despite being a father he is perverted, making Hayate think things he doesn't want to.

It should be noted that Viz has translated the priest's name as "Rean Radiostar". Linn stated that since he is no longer in the dungeon other people will not be able to clearly see him anymore like the scar on his forehead, but Hayate comically states that the mangaka just got tired of drawing it. Before he died, he seemed particularly fond of the Ultima and Dragon Quest series, even to the point of calling himself Akiba's "Lord British".

Appearance
Linn is a priest with short brown hair and orange eyes. He wears a priest outfit. During his first appearance in Hayate no Gotoku!! Episode 3, he has a cross shaped scar on his forehead similar to Shiranui and Ikusa Ayasaki.

Tiger's Den for Butlers
During the time Hayate, Nagi, Wataru, and Yukiji ventured into the dungeon for Hayate's butler training, later followed by Hinagiku and Isumi, Linn appeared before them after Hayate was struck by a poisoned arrow. He helped them by giving information about how to cure Hayate. Later he casually tells Hayate that he already died because of a similar poisoned arrow. It is also revealed that he is the one responsible for setting up the numerous traps inside the dungeon.

During their encounter with Sonia he revealed to the others that she was just an impostor and not the real Sister Fortesia since the real one would be very old. During the fight Linn was mostly just a bystander only pointing out that Yukiji was possessed and helping Hayate use his special move called "Hayate no Gotoku: Like a Hurricane!" Hayate's special move was so powerful that it destroyed the entire church and since then Linn has been haunting the Sanzenin Mansion.

Guiding Hinagiku
On the day of Hinagiku's birthday, Linn also makes an appearance infront of her when she was feeling troubled with her feelings towards Hayate. He tried to guide her feelings and make her realize that she is in love with Hayate, but the conclusion Hinagiku reached was that she was feeling this way because of the unsettled fight when Hayate took advantage of the suspension bridge during the school marathon. However, during her birthday while alone with Hayate on the top of the student council building, Hinagiku did really realize that she has fallen in love with him.

Isumi Being A Maid
During April 1st, Linn appeared in front of Hayate stating that he has decided to go to heaven. But before that he wanted to be with a maid, specifically Maria. But Hayate reminded him that Maria could not see him, giving him ideas of what he could do. Isumi then arrived and offered to help stating it was part of her duties to send spirits to the afterlife. Isumi then wore a maid outfit but Linn said it was not enough since Isumi did not have the soul of a maid. After Nagi tricked Wataru into talking about maids, Isumi learned what was needed to do. Isumi told Linn to watch her carefully as she spun around but she tripped because of her long skirt.

Isumi then proceeded to ask for help from Sakuya who called in her personal maid Haru, actually Chiharu in disguise, to help Isumi become a true maid. Haru easily solved Isumi's tripping problem by telling her to wear a shorter skirt similar to hers, impressing both Linn and Hayate with her simple answer. With that advice and the lesson Isumi learned about fake smiles from Haru, she was ready to fulfill Linn's dreams so that he could move on. Unfortunately after all that hard work, Linn said that it was all just an April's Fool Joke.

Wrote A Love Letter
Despite being a priest he is actually perverted and mischievous. Once he wrote a love letter to Hayate which Nagi said came from a yandere. He became jealous of Hayate because he had to take Maria out on a date as part of Nagi's plan in trying to figure out the one who sent the letter.

At Violet Mansion
He is currently residing in one of the rooms in Nagi's apartment building, which he filled up with his anime and manga collection (which Hayate stated he would destroy). He was only seen recently, breifly, when a new girl inquired about wanting a room, and Hayate accidentally brought her to Linn's room.

After Ruka rents out a room, Linn notes how there was something strange about the Mansion. He later informs Hayate about how the storage room upstairs was notably small compared to the baths which were directly beneath, and how he was unable to pass through one of the walls despite being a ghost. Alice appears shortly after to explain that the wall was protected by a barrier, which made it impossible for him to pass through. Isumi suddenly jumps inside and removes the barrier to the wall, allowing him to pass through. He tells the group that he found corpse-related (initially mentioning the possibility as more of a joke) and is present when the group is suddenly attacked.

Kyoto and Ise Arc
While Nagi is away on a trip to Kyoto, Ruka devised a plan to have interesting experiences without getting in harm's way. While her plan was being carried out, she saw multiple strange ghosts roaming around and she ended up discovering that she was the only one seeing them.

In the end, it was then revealed that the easy to forget ghost priest which is Linn Regiostar was the big culprit of Ruka's 'interesting' experience.

Trivia

 * He has a cross shaped scar on his forehead similar to Shiranui or Ikusa Ayasaki in first appearance, but later the scar is gone
 * In Chapter 92, Hinagiku can see him but in Chapter 360, Hinagiku has lost that ability, but she could "feel" his presence in the mansion.