As I understand it, part of Morrison's point is that superheroes have replaced Abrahamic monotheism. So put this in your vape and vape it, sir: Mary Magdalene has Superman beat by a couple thousand years.
So as I understand it, Morrison's ideas of mythological heroes are less the hero with ten thousand faces. They're more about a figure that takes on slightly different mantels of "heroic" across generations depending on cultural trends, whose values tap into deeper ideals, who sometimes function as wish fulfillment or at least inspiration, and who accomplish feats for good. If I'm misunderstanding this, my apologies in advance.
Issue #1: Inaction Comics #1
Mary Magdalene is mentioned several times in the New Testament's Gospels as one of the most dedicated followers and supporters (including financial) of Jesus. She was most likely a real person. But helpfully for her mythic status, the Bible supplies only the scantiest of details. We mostly learn that she witnessed the crucifixion and the empty tomb, and spread news about (preached!) the latter. Oh, and she had once been possessed by seven demons.
Already in late antiquity, Christians were having none of that.
Issue #2: The White Knight Rises
Whether or not "Gnostic Christianity" was ever a thing, there's a group of texts known as the "Gnostic Gospels." These tell a version of the Christian origin story that turns on the idea of secret knowledge (gnosis) accessible only to the privileged. Some of the oldest ones--late second, third century CE even--are already using Mary to "fill in the gaps" of what we see as the canonical Gospel account, and certainly to drive home the message of secret knowledge.
In the Gospel of Mary, she receives a special vision from God (gnosis!) commending her steadfastness of faith. This responds to the canonical problem that Peter is supposedly the leader of the disciples, but he denies Christ and questions the resurrection. (But don't worry, we also get to see Mary break down in tears when challenged...patriarchy gonna patriarch).
The Pistis Sophia--sophia, wisdom!--pursues a similar line, except Peter gets angrier, Mary doesn't cry, and Christ is even more emphatic that he loves her above the others.
Elaine Pagels relates these versions of the story to questions about how religious authority ought to function in Christianity: is it prophetic and revelatory (gnostic), is it based on a set of previously-acquired knowledge? Which, in these texts, takes on the dimensions of feminine or masculine, wisdom or intelligence, grace or hierarchy. For a new religion that wanted to spread and institutionalize, these were vital question to work out. They struck at the very identity of Christians and Christianity. Mary Magdalene offered a mirror in which Christians on the side of prophecy and grace could see themselves.
Issue #3: Sin City
The next centuries in orthodox Latin Christianity take Mary in a little bit of a different direction. Adopting the Seven Deadly Sins as the primary model for teaching Christian morality, the early medieval Church found it very convenient that seven demons had been cast out of Mary.
Gregory the Great made the fateful move. He asserted that "Mary Magdalene" (Luke 8) who had had seven demons cast out of her was the unnamed sinner of Luke 7 who washed Jesus's feet with her hair was the sister of Martha of Bethany, called Mary (John 11-12). Seven demons plus a sinner...plus this name, Mary? By the tenth century, we're starting to get a full-blown narrative story, a biography, for Our Hero.
The Church yoinked ideas from the legend of Desert Mother saint Mary of Egypt, too. The early Middle Ages thus turned Mary Magdalene into a onetime profligate sinner who turned away from a life of the Seven Deadly Sins. She fled to the desert and spent her life doing penance. In these versions of the Magdalene legend, she models the course of Christian morality. And reinforcing contemporary beliefs about gender, she was linked with the sin of vanity...especially lust, therefore, especially prostitution.
Hitchhiking to the desert might not seem to us like, oh, say, punching Nazis. But Cap didn't need to punch Nazis between 1945 and 2010, either. That's the point of a mythological hero. Diff'rent manifestations for diff'rent generations.
Issue #4: Crisis of Infinite Marys
It's the high and late Middle Ages, however, that will really turn Mary into the world-ranging, superpowered saint you'd write comics about. (Who needs a Golden Age when you have the Golden Legend?) And this is where things get really interesting. Because not only does the era make the Magdalene it needs, but all sorts of different groups within the later Middle Ages cultivate their own heroic Mary.
As Katherine Jansen quickly figured out for her book The Making of the Magdalen, the place you have to start is the mendicant orders of the 13th century, the Franciscans and Dominicans. The justification for the existence of these orders was simple: preaching. 1215 was the year the Church emphatically declared its commitment to instructing lay people in Christianity, and sermons preached by friars were one of the most important strategies.
Remember the whole part about Mary spreading the news of the empty tomb?
Dominicans adopted her as a patron saint. They drew on a French legend in which Mary was persecuted in Egypt and essentially cast out into the wilderness of the Mediterranean Sea to die one way or another...but miraculously, she ended up in France. In this comics universe, she became the apostle to western Europe.
Franciscan brothers had no trouble adopting the apostle Mary as a major saint of their own. But they also tended to emphasize her penitent side. The Mary of the desert, communing with angels, spoke to them of the legend of their founder St. Francis and the seraphim. That is, the momentous encounter where he received his stigmata, a defining moment for Franciscan identity. Mary Magdalene became the exemplar for Francis--he was an alter Christus but also an alter Maria.
But remember, a superhero reflects contemporary ideals. Mary the preacher was the model for male Dominicans, who were permitted to travel and preach. Women were (the ideal went) subject to cloistering. Their religious duties centered around prayer, not preaching.
But Gregory the Great to the rescue! He had lumped in Mary, sister of Martha, with Mary Magdalene, remember. And the 11th-12th centuries had already perfected the dichotomy of Martha and Mary, the active life and the contemplative life. Even while Mary Magdalene embodied the vita apostolica, the purest version of the active life (for men), she could also be the exemplar of the silent, stationary contemplative life. For women.
Not to be left out, the mendicants who turned away from active preaching to study and teach at Europe's new universities also claimed Mary Magdalene. Mary of Bethany had sat at the feet of Jesus and listened to him, so clearly she was the model of study. Clearly.
But that's how symbolic and important Mary Magdalene had become to European Christians by the 13th century. Everyone wanted her.
Everyone--including lay people, who had many and diverse ideas of what to do with this prostitute, penitent, preaching, public, private saint. That's not to draw a sharp distinction between "lay" and "clerical" culture here--legends about Mary are still being recorded by clerics; friars are still keeping their ears to the ground for ideas burbling up among their listeners and confessees.
The point is more, with more people invested in making Mary a reflection of their own identity, her story got a lot more colorful. Craftsmen in the luxury goods production businesses looked to the Mary who supported Jesus out of her resources and the Mary whom Gregory the Great had scorned for her pre-conversion vanity. Friars unhappy with the revelry and tumult of urban life stressed that Mary's sins of vanity included dancing and playing music, urging their flocks to repent of those like their role model had.
And best of all, her French hero legend got a great new action episode involving a shipwreck and a miraculous resurrection of a dead princess (or queen, or governor's wife).
But while this was fun, even it took on special significance in the late Middle Ages. The princess had died in childbirth, so some expectant mothers used little dolls of Mary Magdalene in their birthing chambers as protection during delivery. She even became a model of motherhood.
Throughout late antiquity and the Middle Ages, therefore, we can see people morphing Mary Magdalene into the hero they need her to be. Which, in most cases, bears only the vaguest of resemblances to the original biblical source material.
Issue #5: The Watchmen
And you might consider later 20th century iterations of Mary as well. In particular, the modern--secularized!--western view of Mary is fascinated with the idea that she was Jesus's wife, or at least, that the two of the had some kind of sexual relationship. That can be explicit--Da Vinci Code--or it can be The Thing That We'll Say Everything But--Jesus Christ Superstar, where Mary is a prostitute but plays the closest thing to a love interest ("I Don't Know How to Love Him" much?).
This is, of course, our version of deconstructing the Christ story. How would it really play out, we ask? (according to our modern understanding of 1st century Judea, that is). And Mary is, yet again, the hero onto whom we map the central anxiety that we see in the narrative today.
Whether we want a Jesus we can relate to or want a Jesus we can knock down off the Christ pedestal or just want another girl in the God story, Mary Magdalene is still our mythological hero.
She might not be punching Nazis or flying around the world--or even crossing the Mediterranean--but she's tapping into our ideals and spiritual needs.