As an archbishop, he wore a golden robe.
Of the three Archbishops, he is the most calm and collected.
Whilst living in the old Holy City, he became a believer after witnessing Pope O'Brien conduct a cleansing ritual nearby a still in construction monastary next to a new stone church.
During the assault of demonic hybrids, Mayne stood atop of Cathedral and observed the entire battle together with archibishops Tayfun and Heather. As they expected, Four Kingdoms' forces were destroyed leaving their borders weakened. However, to acquire this they had to sacrifice many of Judgement Army as well. Mayne bitterly said if there was other plan as fast as this he wouldn't send warriors to hell. When two archbishops left after a short clash he mused about god preferring winners.
Not long after this, he approached the incarcerated King of Graycastle and happily informed him of the state of his country and actions of his children, shortly before poisoning the King to death. In his final moments the King cursed both Mayne and the Church to hell for what they had done to him and his family.
After the overthrow of the Queen of Everwinter Mayne, Heather and Tayfun discussed situation in Kingdoms of Everwinter and Graycastle. Roland's conquer of Longsong Stronghold and return to Border Town piqued his interest. When Heather delivered rumors about Witch Cooperation Association recruiting new witches, they discussed whether it was related to Roland or it was coincidence. Mayne swore to lead God's Punishment Army in case it was the former.
This never came to be though. Not long after Heather had left for Everwinter to take control of the local situation, they received word that Garcia Wimbledon had abandoned Greycastle and set her sights on Everwinter. Arriving at the Kingdom, her Blacksail fleet cut a bloody path through the Church, eventually taking control of the Kingdom and allying with the King of Wolfsheart. Heather's ring was returned to the remaining two Archbishops, still attached to her severed finger after she had been brutally tortured to death.
Her death angered Pope O'Brien, who tasked Mayne with taking control of the two Kingdoms with the help of two Purified Witches, Zero and Isabella and a demonic siege weapon the church had stored that was taken from the devils some time in the past. Not long before the final battle, Mayne witnessed Zero's sadistic treatment of some of the prisoners as she toyed with them, causing him to vow that he would make her more obedient once he became Pope. After Zero had managed to absorb both the King of Wolfsheart and Garcia, though the latter managed to fight back better than most.
Shortly before Pope O'Brien passed away he led Mayne to the Pivotal Secret Area and allowed him to witness the truth of the Church, through use of a magic stone that had recorded the past meeting of Alice with her Council as they decided to go forward with their plans. This news greatly shocked Mayne, even more so when O'Brien admitted that succeeding generations had betrayed their founders by usurping the position of Pope from the Witches, as it was a rule set down by Alice that only they hold the position. With his last breath, the old Pope apologised for leaving such a heavy burden to him, and remarked that "even giving up ... may also be a wise choice".
His tenure as Pope was to be all too brief however. After learning the truth, Mayne seemed to become more paranoid and sought to create an escape for himself if things turned bad. After killing Garcia, he held onto her Blacksail fleet and crew in secret, intending to run away to the Fjords to live out the rest of his life if necessary.
Not that it mattered, as soon after his one presiding meeting with the three Archbishops, he was attacked by Zero who initiated the Battle of Souls against him, after having Isabella negate his God's Stone of Retaliation. Realizing that they alone couldn't have done all of it, he too late came to understand the true meaning behind O'Brien's last words and apology. Wracked with guilt, the old Pope all along had intended for a Witch to regain the Pope's position that had been unjustly stolen, making Mayne nothing more than a sacrifice to empower Zero, ironically not too dissimilar to how they had treated the Witches used to create God's Punishment Army. Although he fought back, he was ultimately beaten and absorbed by Zero.