On October 12, 2018, it was reported that Priest had signed a contract with WWE; six days later he was formally introduced, among other new members to the NXT brand. On November 28, at an NXT TV taping in Winter Park, Florida, he made his debut as a heel under the name Punishment Martinez, losing to Matt Riddle. On April 15, 2019 it was reported that Martinez would be repackaged and go by the new ring name Damian Priest. Vignettes began airing starting at NXT TakeOver: XXV in June. He made his in-ring redebut on the June 19, 2019 episode of NXT, defeating Raul Mendoza. On the July 24 episode, he defeated Keith Lee. On the October 2, episode of NXT Priest would start a feud with Pete Dunne when he attacked him after his match. This led to a match between both of them on October 16 episode of NXT, which was won by Priest. A rematch was held between Dunne and Priest where Dunne defeated Priest, however after the match, Killian Dain attacked both men. On the November 13 episode of NXT, a match between Dunne and Dain was scheduled on the night. However, Priest attacked Dain and subsequently, a brawl occurred between the three. This eventually led to a triple threat match at NXT TakeOver: WarGames for number-one contendership for the NXT Championship. Priest and Dain were both defeated by Dunne in that match. Priest would also become a part of the 5-on-5-on-5 Survivor Series pay-per-view match, representing team NXT, where he was eliminated when Randy Orton pinned him after countering Priest's finishing move The Reckoning an RKO. On the December 18th episode of NXT, Damian Priest defeated Killian Dain. On December 25th episode, Priest teamed with Tony Nese against the team of Keith Lee and Lio Rush in a losing effort. Priest was nominated for NXT Year-End Awards 2019 under the category "Breakout Star of the Year Award", which was won by Keith Lee.
On January 8, Damian Priest competed in a Fatal 4-Way match to determine the number one contender for the NXT North American Championship, with Keith Lee, Dominik Dijakovic and Cameron Grimes as the other 3 competitors, which was won by Lee. On the 29th January episode of NXT, Damian Priest interrupted the then-NXT North American Champion Keith Lee, saying that "he liked taking things", and expressed his wish to take the NXT North American Championship from Lee. However, Dominik Dijakovic also interrupted and subsequently a match was held between the two, where Priest lost to Dijakovic. Priest then attacked Dijakovic using a nightstick during his match against Cameron Grimes, continuing their rivalry. On 11 March, 2020, Priest attacked Keith Lee after his match against Grimes using the same nightstick and then got away through the crowd the same way he got away when he attacked Dijakovic previously. On the March 25 episode of NXT, Priest made his intention to win the North American championship clear. The promo subsequently transitioned into a brawl between Priest, Lee and Dijakovik. On April 1, Priest became a part of the triple threat match for the North American Championship in a losing effort, with Lee successfully retaining the title.
On the April 22, 2020 episode of NXT, Finn Bálor was attacked backstage by an unknown attacker, which resulted in his removal from his scheduled match against Velveteen Dream. The next week, a video footage was shown of Bálor’s locker room looking disheveled and he was gone. After he issued a warning to the attacker, Bálor was scheduled to be in a match against Cameron Grimes on May 13, 2020. During their match, Damian Priest distracted and attacked Finn Bálor using a nightstick, resulting in Grimes defeating Bálor. After this match, Priest revealed that he was the unknown attacker. Priest then challenged Bálor for a match at NXT TakeOver: In Your House, which Bálor accepted. In that match, Priest was defeated by Bálor. Following their match, Priest praised Finn Bálor in a backstage interview and accepted that he was humiliated, no excuses, and also said that it was just the next step for Priest's name to live forever, turning into a fan-favorite in the process. On the June 10, 2020 episode of NXT, Cameron Grimes flaunted his previous victory over Finn Bálor and deemed Priest as a "loser" in a backstage interview, leading Priest to attack him, confirming Priest's face turn. The next week, Priest faced Killian Dain in a singles match, which he won. After the match, Priest was exiting the arena, and was furious to see all the tires of his Dodge Challenger punctured, which was done by Grimes, and he mocked Priest after this again, setting up a match between the two for the next week, but Priest was attacked in the parking lot before the show began, thus injuring him, which resulted in Grimes defeating Priest. At NXT The Great American Bash's first night, Priest then challenged Grimes for a rematch. Grimes however, said that he didn't had time to worry about the past, and looked towards moving ahead from Priest. After a promo by Priest, a rematch was held between the two, which was won by Priest.
After this, Damian Priest again started to pursue the vacant NXT North American Championship, and was scheduled to be in a triple threat match involving himself, Oney Lorcan and the returning Ridge Holland, the winner of which would be given a spot to win the title in a ladder match at NXT TakeOver: XXX. Priest won the qualifier match the next week and he was added to the ladder match at NXT TakeOver: XXX, as one of the five competitors. At NXT TakeOver: XXX, Priest won the NXT North American Championship, marking his first championship win in WWE. Priest then had a successful title defense against Timothy Thatcher and then another successful defense against Johnny Gargano at NXT TakeOver: 31. On the October 14 episode of NXT, Priest then successfully defended his title against Dexter Lumis, but after the match, he was attacked by Gargano by a steel chair, leading to a rematch for the title between the two at NXT Halloween Havoc, the stipulation of which would be decided by a wheelspin on the spot. During their Devil's Playground match, Priest was attacked by an unknown masked character with a steel pipe. As a result, Priest lost the title to Gargano, ending his reign at 67 days. Gargano however, lost the title to Leon Ruff just two weeks later, due to a distraction during the title match by Priest. Ruff retained the championship in a rematch against Gargano the next week by disqualification, when Priest punched Ruff during the match, thus disabling Gargano to win the championship. This soon transitioned into a triple threat match for the NXT North American Championship which would take place at NXT TakeOver: WarGames. During the match, Damian Priest was again attacked by the same masked character that attacked him previously at Halloween Havoc, who was revealed to be Austin Theory. As a result of that, Priest lost the match, with Gargano winning the title by pinning Ruff.
On the December 9 episode of NXT, Priest looked forward to take revenge from Austin Theory following his attack at WarGames, however, he was viscously attacked by a returning Karrion Kross from behind, after which Priest had to be helped out of the arena. The next week, Kross challenged Priest to a match at NXT: New Year's Evil, which Priest accepted. In that match, Kross defeated Priest.
Priest made his next appearance in the 2021 Royal Rumble match, entering at number fourteen. He eliminated four participants (John Morrison, The Miz, Elias and Kane) before getting eliminated by Bobby Lashley. The following night, Priest made his Raw debut after being introduced by Bad Bunny during a Miz TV segment. He would then face The Miz and win by pinfall. The next week on Raw, he defeated Angel Garza in another singles match. On the February 15 edition of Raw, Priest helped Bad Bunny win the 24/7 Championship by knocking out Akira Tozawa, who pinned R-Truth moments before. In subsequent weeks, Priest racked up a winning streak by defeating Angel Garza, Elias and Jaxson Ryker, however, The Miz and John Morrison continued their rivalry against Bad Bunny and Priest, after The Miz attacked Bad Bunny using a guitar after Priest's match against Ryker. Priest and Bad Bunny then challenged The Miz and Morrison to a tag team match at WrestleMania 37, which they accepted. At WrestleMania, Priest and Bad Bunny defeated The Miz and Morrison.
On the next night, the Raw after WrestleMania, The Miz and Morrison challenged Damian Priest to a two-on-one handicap match, where, despite dominating most of the match, Priest lost due to outside interference by Maryse, making it his first loss on the main roster. In the subsequent weeks, Priest won singles matches against both The Miz and John Morrison, and also won a tag team match, teaming up with The New Day against The Miz, Elias and Jaxson Ryker. Eventually, conflicts also started arising between the Miz and John Morrison themselves, although they continued their rivalry with Priest, eventually setting up a lumberjack match between The Miz and Priest at WrestleMania Backlash. In that match, Priest defeated The Miz. The next night on Raw, Priest also defeated John Morrison in a lumberjack match. Briefly afterwards, he took time off due to a back injury. After making a few minor television appearances, Priest made his return on the July 19 Raw by saving Humberto Carrillo, when Carrillo was being attacked by Sheamus after their title match. Following this, Priest and Sheamus had a match on Raw, where Priest defeated Sheamus. This started a rivalry between the two men and they continued to face off each other; Priest would soon challenge Sheamus to a match at SummerSlam for the United States Championship, which Sheamus accepted. At the event, Priest defeated Sheamus to win the title. Priest then successfully defended his title against Drew McIntyre and Sheamus, earning McIntyre's respect in the process. Subsequently, a singles match was held between McIntyre and Sheamus to determine the number one contender for Priest's United States Championship, which was won by Sheamus, setting up a rematch for the title between the two at Extreme Rules. Eventually, Jeff Hardy also became a contender for the championship after defeating Sheamus, turning the title match at the event into a triple threat; Priest successfully retained his title at the event. The next night on Raw, Priest again defeated Sheamus in a no disqualification title rematch.
On the October 25 Raw, Priest won a match against T-Bar by disqualification, when the latter threw a chair at the former outside the ring. After this, Priest viciously attacked T-Bar. The next week, T-Bar attacked Priest with a kendo stick during their match, due to which Priest again attacked T-Bar in a similar fashion, further developing his new vicious character and mannerisms, before getting challenged by Apollo Crews. On the November 22 Raw, Apollo Crews once again confronted Priest before Priest successfully defended his title against Sami Zayn. After Priest's defense against Robert Roode, Roode's ally Dolph Ziggler attacked Priest, starting a small rivalry between Priest and The Dirty Dawgs. On the January 17, 2022 episode of Raw, Priest lost to Kevin Owens in a non-title match, which marked his first clean loss on the main roster. As a result, Owens received a match for Priest's United States Championship on Raw the following week, which he won by disqualification, but Priest retained the title. Priest was a part of 2022 Royal Rumble match, entering at number seven; he scored no eliminations and was eventually eliminated by Omos. In the subsequent weeks, Priest successfully defended his title against AJ Styles and Shelton Benjamin, before getting challenged by Finn Bálor. On the February 28 episode of Raw, Priest lost to Bálor, ending his championship reign at 191 days, following which Priest fully turned heel for the first time since May 2020.
At WrestleMania 38, Priest made an appearance by distracting AJ Styles during his match against Edge, causing him to lose the match. After the match, Edge celebrated his victory with Priest, starting an alliance between the two. Over the following weeks, they continued to feud with Styles, further developing new mannerisms and character. On the April 25 edition of Raw, Edge and Priest were dubbed The Judgment Day, after which Priest defeated Finn Bálor in a singles match. At Hell in a Cell on June 5, The Judgment Day (Edge, Priest and the newly recruited Rhea Ripley) defeated Styles, Finn Bálor and Liv Morgan in a six-person mixed tag team match. The next night on Raw, Edge introduced Bálor as the newest member of The Judgment Day; however, Bálor, Priest and Ripley suddenly attacked Edge, kicking him out of the stable. The Judgment Day then began a feud with the Mysterios (Rey and Dominik) in an attempt to recruit Dominik into their ranks. At SummerSlam on July 30, Priest and Bálor were defeated by the Mysterios following interference from a returning Edge. At Clash at the Castle, Priest and Bálor lost to Edge and Rey Mysterio in a tag team match, where Dominik turned heel on both of them to join The Judgment Day. On November 5, at Crown Jewel, Priest, Bálor, and Dominik defeated The O.C. (AJ Styles, Luke Gallows, and Karl Anderson) in a six-man tag team match after interference from Rhea Ripley. On the November 28 episode of Raw, The Judgment Day defeated The O.C in an eight-person mixed tag team match to end their feud.
On the January 9, 2023 episode of Raw, Priest, Bálor and Dominik won a tag team turmoil match for a Raw Tag Team Championship opportunity against The Usos. At Raw is XXX on January 23, The Usos successfully defended the championships against Priest and Dominik despite Jimmy Uso's injury, with Sami Zayn taking Jimmy's place. At the Royal Rumble on January 28, Priest entered the Royal Rumble match at number twenty-two, but was eliminated by the returning Edge. Afterwards, Priest and Bálor eliminated Edge with help from Dominik. On the February 6 episode of Raw, Priest defeated Angelo Dawkins to qualify for the Elimination Chamber match for the United States Championship. At Elimination Chamber on February 18, Priest failed to win the title inside the namesake structure.
On the Raw after WrestleMania 39, Priest got involved in Dominik's confrontation with Bad Bunny, Priest's former tag partner; Priest ended up chokeslamming Bad Bunny through the announcer's table. Bad Bunny returned on the April 24 episode of Raw and challenged Priest to a San Juan Street Fight at Backlash. Priest would lose the match at Backlash after interference from the Latino World Order, Carlito, and Savio Vega. On May 7, Priest, alongside Bálor, were selected as the Raw participants for the new World Heavyweight Championship tournament. However, Priest lost his qualifying match to Seth "Freakin" Rollins in the quarterfinals round on the May 8 episode of Raw. Rollins went on to become the inaugural World Heavyweight Champion at Night of Champions. On the June 5 episode of Raw, Priest unsuccessfully challenged Rollins for the World Heavyweight Championship. Priest defeated Matt Riddle to qualify for the men's Money in the Bank ladder match on the June 12 episode of Raw. At Money in the Bank, Priest successfully retrieved the briefcase after delivering a Broken Arrow to LA Knight off the ladder and won the match. Later that night, Priest appeared halfway through the World Heavyweight Championship match between Bálor and Rollins. Priest's presence distracted Bálor enough for Rollins to take advantage to win the match to the irate of Bálor.
At Payback on September 2, Priest and Bálor defeated Kevin Owens and Sami Zayn to win the Undisputed WWE Tag Team Championship after interference from Dominik, Ripley and JD McDonagh. On the September 25 episode of Raw, Priest and Bálor defeated Owens and Zayn in a rematch to retain their titles. At Fastlane, Priest and Bálor lost the Undisputed WWE Tag Team Championships to Cody Rhodes and Jey Uso after JD McDonagh accidentally cost Priest and Bálor the match. They regained the titles from Rhodes and Uso on the October 16 episode of Raw. At Crown Jewel on November 4, Priest attempted to cash in on Seth Rollins after his successful title defense against Drew McIntyre, but Zayn stopped him and ran off with the briefcase before he could officially do so. Later that night, Priest lost to Rhodes despite interference from Bálor, Dominik, and McDonagh. On the November 13 episode of Raw, Priest and Bálor defeated Rhodes and Uso in a rematch to retain their titles after interference from Drew McIntyre. On the November 24 episode of SmackDown, Priest and Bálor successfully defended their titles against The Street Profits (Angelo Dawkins and Montez Ford). The next night, at Survivor Series WarGames, Priest participated in his first WarGames match alongside The Judgment Day against Rhodes, Rollins, Uso, Zayn and the returning Randy Orton in a losing effort. On the December 18 episode of Raw, Priest and Bálor successfully defended their titles against The Creed Brothers (Brutus Creed and Julius Creed). At Royal Rumble on January 27, 2024, Priest entered the namesake match at number twenty-six, eliminating R-Truth before being eliminated by Sami Zayn. On the following episode of Raw, Priest and Bálor defeated DIY (Johnny Gargano and Tommaso Ciampa) to retain their titles. At Elimination Chamber: Perth on February 24, Priest and Bálor successfully defended the titles against New Catch Republic (Pete Dunne and Tyler Bate). On night one of WrestleMania XL on April 6, Priest and Bálor lost the SmackDown Tag Team Championships to A-Town Down Under (Austin Theory and Grayson Waller) and the Raw Tag Team Championships to The Awesome Truth (The Miz and R-Truth) respectively in a six-pack tag team ladder match, ending their second reign with the titles at 173 days.
The following day, on night two of WrestleMania XL, Priest successfully cashed in his Money in the Bank contract on Drew McIntyre to win the World Heavyweight Championship following an attack by CM Punk, becoming the second person to cash in at WrestleMania. At Backlash France on May 4, Priest successfully defended his title in his first title defense against Jey Uso after interference from Bálor and McDonagh, despite asking them not to interfere. At King and Queen of the Ring, Triple H announced that Priest would defend his title against Drew McIntyre at Clash at the Castle: Scotland, in the latter’s home country. At the event on June 15, Priest successfully retained the title against McIntyre after interference from CM Punk. On the June 17 episode of Raw, Priest challenged a returning Seth Rollins to a title match at Money in the Bank, which on the following week's Raw gained a stipulation that if Rollins lost, he would be unable to challenge Priest for the title as long as he held it. but if Priest lost, he would be forced to leave The Judgment Day. At the event on July 6, Priest successfully defended his title against Rollins and McIntyre, the latter of whom cashed in his newly won Money in the Bank briefcase during the match, but was attacked by Punk. Priest subsequently pinned McIntyre to retain his title. After Clash at the Castle, Priest began showing more respect to his opponents as his crowd support gradually increased, teasing a face turn. At SummerSlam on August 3, Priest lost the title to King of the Ring winner Gunther via technical submission after Bálor turned on Priest, ending his reign after 118 days and fully turning Priest face for the first time since February 2022. On the following episode of Raw, Bálor officially kicked both him and Ripley, who was also betrayed by Dominik for Liv Morgan, out of the group, cementing his face turn. During Priest's match against McDonagh that night, Bálor ambushed him along with the rest of The Judgment Day, until Ripley came out to save him. Priest and Ripley would afterwards embrace each other, thus staying together as a team and going by The Terror Twins. At Bash in Berlin on August 31, Priest and Ripley defeated Mysterio and Morgan with Ripley pinning Morgan, despite interference from The Judgment Day. At Bad Blood on October 5, Priest defeated Bálor despite interference from Carlito and McDonagh. On the November 4 episode of Raw, Priest defeated Dominik Mysterio, Seth "Freakin" Rollins and Sheamus in a fatal four-way match to become the number one contender for the World Heavyweight Championship. At Survivor Series: WarGames on November 30, Priest failed to regain the title from Gunther after interference from Bálor.