Hi there everyone!
When I see "mythopoeic" I think "mythopoietic," "myth-making." Tamrielic myths seem to retell themselves over and over again in anologous forms - for example, as told in the Nu-Mantia Intercept, the Adamantine Tower, where the divines literally set the world in stone, is followed by the Red Tower (Red Mountain), where Lorkhan's heart provides the divine presence needed to congeal Nirn, which is in turn followed by Walk-Brass Tower (presumably Numidium), White Gold Tower, the Marukhati Selectives and their tower, and so on, all of which were created with the intent of effecting some great physical, metaphysical or political change.
What is salient here is that ever since the Adamantine Tower, towers literal and metaphorical have played central roles in shaping and reshaping Mundus. And the Nu-Mantia Intercept seems to suggest that all of the later towers and their associated stories are metaphysical echoes of the Adamantine Tower and its singularly important story. There are references to the formative power of myth elsewhere as well, like the "Mythic Aurbis" account in The Monomyth ("The magical beings of Mythic Aurbis live for a long time and have complex narrative lives, creating the patterns of myth."). Everything I've read has given me the impression that the experience of the et'Ada, what Dagoth Ur calls the "divine dreamworld," is in some sense nothing but a collection of mutually disjoint stories, like what mortals experienced during the Dragon Break.
In any event, if myths as such do have this cosmic power, then it's entirely reasonable that a myth-making device should be able to, say, cause an entire race of people to instantaneously vanish from the face of Tamriel. And if stories are really that important to the existence of the et'Ada, then maybe a myth-making device is exactly what's needed when you want to tinker with the heart of a god.
Anyway, that's what I think "mythopoeic" probably means.
Yup, yup. actually, I think there are many more examples of "mythopoeic"events.
In the Monomyth for example, it is said that some of the et'Ada told the "ultimate story: that of their own death". Tiber Septim reenacted (as already said) the event when Auriel ripped out Lorkhan's heart. Zurin Arctus was his victim, result was the Mantella.
Auriel -> Lorhkan -> ripped out heart
Tiber -> Zurin -> ripped out heart
The Tribunal, the Dwemer, Dagoth (see Allerleirauh's post on that topic)
In a more vague way: Uriel Septim and Jagar Tharn, there was also a heart, in this case Tharn's Jewel of Fire, involved. Perhaps even the Nerevarine and Dagoth Ur. Spinning that thought a little bit further, this leads to the assumption that ascendance (though not always godhood, perhaps a better way would be to say gain advantage or domination) was in these cases gained by the suffering of others.
Auriel benefited from the suffering of Lorkhan
Tiber from Zurin
The Tribunal and Dagoth Ur from the Heart of Lorkhan
The Dwemer from the Heart of Lorkhan (Allerleirauh again)
There's surely more, though I think it's clear that there seems to be a connection. Perhaps that's what is meant by "reach Heaven by Violence", or at least a part of it.
There are other instances where the retelling of mythic events plays a major role.
Lorkhan [censored] Nirn -> Molag Bal [censored] Vivec
Vivec in effect worked a lot of mythopoeic magic, storytelling magic, storymaking magic. He retold his whole life's story. On a sideline: in his Sermons, Vivec fights eight monsters. Is the number eight truly a coincidence here or does he tell another story?
The Maruhkati Selective did it, too, imho, though they chose a pretty large scale. They tried reenacting the creation itself to separate the elven aspect of Akatosh, Auriel from the entity of Auriel-Akatosh.
Sorry for not quoting sources, I'm getting lax.