For his upcoming album, King started by writing down a list of characters, set them in a house where strange things are going on, and got the powers of darkness involved. The result was the album "Them", which was released in June 1988 and sold over 200,000 copies in the USA, making of it his best selling album yet (and "Abigail" being ranked in second place). After the recording sessions of "Them" at M.M.C. Studio in Copenhagen, as Andy already packed his gear and went back to Sweden, King and producer Roberto Falcao realized that they were lacking some very important harmony guitars in a song. The parts were pretty simple so King may have played it, but since that mistake, the band established a new recording procedure; making up a little blackboard with the song titles on it, and underneath each title is everything that is supposed to to go into the song; who does solos, is there any keyboard parts, etc. When a part is done, they just cross it out, so they make sure everything is completed and that a mistake like this one would not happen again. There was a bonus track on the CD version only of "Them"; a track called "Phone Call", which is actually a moody horror piece containing no music, but only a phone call from King's deceased grandmother, which helps further painting the gory details told on the story of the album. Back in those days, many journalists asked King if the events of the story were based on something from his own childhood since the main character is named King, but he always kept the answer for himself only. "Them" got its huge success, mainly due to the MTV video hit "Welcome Home" that was shot in an old castle just outside London, England. This video, which was the first real song of the album after the intro “Out From The Asylum”, used little things from the whole story, except for that girl which was not even a part of the story. Even though her presence didn't made much sense, she was put there because a beautiful girl had to be in video clips at that time. For the following tour, there was a big house from that story, which was built in Sweden, as well as an actress portraying the character of Grandmother, so it was something really different to see. The shows became more theatrical, and it was really the goal that King wanted to reach, as he simply wanted to scare people.

At one of the shows, some witches had come to a show, and invited King to meet Anton LaVey at the church in San Francisco. It was the first time that King would meet the writer of "The Satanic Bible", who is also the founder of the Church Of Satan. King spent the whole night there; he saw the ritual chamber which had been locked off for two years re-energizing itself, and had an hour-and-a-half talk with LaVey, just both of them in that ritual chamber, while some very special things happened in there. King told him what he felt about Satanism, what it is and what it is not, in his opinion, instead of LaVey talking and King nodding his head. At this point, King then asked him what he's been thinking of it. LaVey then took the Baphomet symbol off his jacket and pressed it into King's hand, which King recalls as an unbelievable experience. They took some pictures, and LaVey played keyboards for King, singing "Wonderful, Wonderful Copenhagen", something which King would never forget. Since then, King have written personnal letters, as he was told he could call him any time, day or night, if he just wanted to chat or whatever, but King's not a person who takes advantage; he has too much respect. They both have been corresponding by letters for a little while. The contents of those letters is so strong and so meaningful that King would never show them to anybody; it mentions some real deep stuff, and a lot of mutual respect. Since then, King was mentioned in LaVey's biography, some magazines and stuff like that. He went out with Zeena, LaVey's daughter, a couple of times, who is a very nice girl, even though King didn't know her that much. At first, King didn't know if LaVey was for real, if he meant what he wrote or if it was just a hoax to make some money, but King certainly confirmed that LaVey was sincere and that he had the same views; the Satanism is not a religion at all; it's life philosophy.

At the time, Geraldo Rivera, famous host of the sensationalism TV show "Geraldo", made a special program about satanism in which participated Zeena LaVey. King also participated to the the show, as a crew was sent down to Florida where King Diamond was performing that day and they shot a little bit of the gig. What pissed off King is that they also filmed a 45-minute interview with him, and they ended up using only a few seconds before saying that King was saying bullshit. For sensationalism, they only picked one line out of its context where they could say it's bullshit, so it just ended being nothing. It would have made so much more sense otherwise.

In the following October, King released a compilation EP called "The Dark Sides", which contained a few rare tracks such as "No Presents For Christmas", "Shrine", "The Lake" and "Phone Call". Following that release came a lawsuit from Gene Simmons' lawyers, the famous bassist of Kiss. In that letter, it stated that they had reasons to believe that the make-up King used on the cover of "The Dark Sides" was based upon the make-up Gene used to wear in the seventies and early eighties with Kiss. It completely surprised King, who never ever heard anyone in his life saying that there would be a similarity with Gene's make-up. That statement also accused King to immitate the old Kiss shows. However, the difference between both shows is huge; Kiss used props such as fire-breathing, blood-spilling, fire alarms, etc, and on his side, King Diamond shows are totally theatrical with story characters on stage, just like a theatrical act. The lawyers of both parts worked a deal out of court, otherwise it could have taken years to solve the case, which didn't interested King much. That deal forced King to modify his make-up, which he already been changing anyway for the next album. Even though King found it pretty ridiculous, and that even now he's still a bit bitter about it, it gave him some publicity. King should actually thank the press big-time because they ridiculed Kiss for that and pretty much put a stop to it. However, King used to like Kiss a lot and this haven't changed since, regardless off whether Gene Simmons tried to sue him or not; he still respects Gene and Kiss anyway. King prefers taking things positively than running around being negative.

With that new make-up, King decided to take it a little further and tried to incorporate blood in the makeup. It was real fancy, but hard to put on everyday, as it was lots of job filling in these white spots with the black pattern then adding blood. However, King always used to put it all by himself since the beginning. He sits there, with a cup of coffee and a cigarette, and an hour later, he's done. Only once he had the help from two girls brought by the label, in order to help King, but it turned more into a disaster as King truly hated it. It was during a photo session in England for Kerrang! magazine. King finds it much more faster and easier to do it himself as he knows extremely well his face and he's used to put his own make-up himself since those years.

After the release of "The Dark Sides", Mikkey left the band; he asked too much money and the band couldn't afford it, so he decided to leave. On his side, Mikkey claimed he left the band because he was pissed off to see that King had to be the only star in the band, and that the other guys just had to be quiet, without any credit and being only musicians, not to be truly a part of the band. There were many arguments between King and Mikkey back then, but they became friends again some time later. The new drummer was Chris Whitemeier. Even though he was not a bad drummer, Chris have quickly been fired as he wasn't creative enough.

As King was still looking for a new drummer for the recording of his upcoming album, he hired temporarily Mikkey as a session drummer, but for the recording sessions only. For the first time, the recording sessions took place in the USA, as the album was recorded at Rumbo Recorders, Canoga Park, in California. It was very convenient for the band to record there as it was right around the corner of where they were now living since a year and a half, in Los Angeles.

It often happened that something weird occured in the studio and nobody couldn't explain it, and it happened also during the making of this album. During the recording sessions, King worked with his friend and producer Roberto Falcao, as well as with Gina Immel, an assistant engineer, who had been scared to death from many things. Once, they spent all day in the studio recording mainly the vocals. At night, King was with some friends in a small room next door and King was testing new riffs for some scary parts of the album; as they stood there, suddenly bursts in this woman, pale looking, scared to the bone, saying that she could clearly hear King's voice coming out of the console, while there were no tapes on any of the recorders. She told them the lyrics she could clearly distinguish coming out of the console and they realized that she was describing the lyrics they were testing outside the studio. But what was really amazing was that they've never recorded this stuff. Then entered another girl saying that she had heard exactly the same thing. They checked the console to see if it was due to parasites, but they came to the conclusion that it was King's voice. Another time, after they have finished up the recordings, King and Roberto were at the studio mixing the vocals. During that, they wanted to mix a riff, but they just couldn't find it, it had disappeared! Roberto was terrified and kept asking King whether it was one of his pranks, or whether he had forgotten to record it or anything that crossed his mind. But King was certain that he had recorded this riff and that it couldn't have been erased. Eventually, this riff does not exist in the album; it's gone. They also had tape recorders turn themselves on, a trash-can move by itself; a lot of weird stuff happened there.

King recalls Gina sitting in the corner of the studio, writing in a book all the time because Roberto was doing everything and they didn't really need her help much. One day, King asked her what she was writing in that book all the time, and she replied it was just a little diary of what was going on in the studio. At the end of the sessions, King asked her if he could have a copy, which he found very funny and that he still has somewhere now, in which she had written down some interesting comments like "I can't believe they're late again, we're supposed to be here at 12:00 and it's 2:00 now, so I guess they have enough money in the budget", or stuff like "Roberto's getting pretty drunk again".

After all these things, the album finally came out in August 1989. Called "Conspiracy", it was the sequel of the story told on "Them". It was during the tour for "Them" that King realized that that story was not finished. He had so many more ideas that just came flying in his head that he had to finish the story and continue on with all those new ideas. However, "Conspiracy" didn't sold as much as its predecessor, but quite well though. The original cover art for the album depicted King at the gates of Amon, throwing a coffin out. King wasn't too pleased with the artwork and the covers were destroyed, however a few survived and are highly sought after today and are quite possibly the rarest King Diamond collectable. The cover was replaced by a simple picture which showed King with his bloody make-up. Once again, the cover of the album made some controversy as it has been censored in a few countries, such as Korea. In this country, the cover shows only the King Diamond logo as well as the title "Conspiracy" written at the bottom.

For the upcoming tour, King needed a permanent drummer, so during the same month, in August 1989, after having auditioned more than 40 drummers from all over the world, Snowy Shaw entered the band. The times of the audition for Snowy were quite tumultuous. Snowy, who just turned 21 that summer, had to go to Los Angeles for the audition. After some major rock'n'roll style turmoil at the airport in Copenhagen where Pete Blakk and Snowy met up with bassist Hal Patino, the three of them, completely drunk, managed to get thrown off the L.A. flight once they had boarded the already 10-hour delayed flight one hour later than the rest of the passengers, who applauded when Police got on the plane and lifted the three off. The one and only obnoxious Pete somehow got TWA to compensate them with dinner and hotelrooms, where they immediately emptied the minibars at expense before they did the clubs downtown. The following day, Pete apologized to the TWA manager and they got on the plane and finally arrived in L.A. two days later than planned, where they got picked up at the airport by King's manager, Olé Bang, in a big convertible Cadillac and droven back to their homes in Canoga Park where a neighbourhood party was going on. At Mates rehearsal studios, where Guns N' Roses rehearsed next door, Snowy started the intro fill for "Welcome Home" and the band quickly ran through two songs, then King turned around and gave Snowy thumbs up. That evening, they went to celebrate at Rainbow and other clubs at the sunset strip, where thousands of rockers were lined up, one flashier than the next. The next morning, the band went to Hollywood, in an old movie studio, to shoot the luxerous video for "Sleepless Nights" in a classic horror style. At first, the idea of shooting a black and white video left King perplexed, but mixed with old horror movies footages, it really gave the feeling that the whole thing was filmed at the same time.

On that tour, the shows ended with the song "Cremation", just like on the album. During that song, people opened the end of a coffin brought on stage and did slide this little board out, where King lied down on it. There was a little window in the side of it that was open so he could get out, which you can look under all the time. At some point, they took off the lid and somebody brought out a lighted torch, and they'd torched the inside of the coffin. Flames then started to arise from the inside of the coffin while you could still look right under it, and all that was left was a skeleton that was still burning... and King was just gone. It was a trick people really enjoyed, and that he kept doing for some other King Diamond tours after that. Those tricks not only worked out well, but were also already planned since the beginning, as King recalls having written parts of the album with pretty much the live show in his mind.

Around that period of time, King moved back to Denmark as he couldn't live in Los Angeles. He always been able to easily adapt to other cultures and customs, but living in Los Angeles was not really made for him, even though he tried to live there for a year and a half; it was just too superficial for him, too much different from the life he used to live before. However, he still loves going there for a week or two, but then he needs to get out.

During the European part of the tour in early 1990, Snowy broke his leg at a show in Spain, but was still able to complete the remaining dates with no bigger problems. A short time later, on March 9th 1990, Mercyful Fate almost reunited for a single time as Hank, Michael and Timi joined the King Diamond band on stage for a jam on the last day of the "Conspiracy" tour, which took place in Copenhagen.