ascendere = ad + scandere, just as descendere = de + scandere. (scandō, scandere = to climb) . So it seems appropriate to recognize the roles of the two Latin prefixes in the way we often do in English: climb up, vs. climb down.
A month later: "climb up" is still not accepted.
Nor is "go up."
There are many reasonable interpretations. Jungian psychology uses "the shadow" as a sort of personification of one's own subconscious/id. He believed people needed to, more or less, confront this aspect of themselves and overcome it. In talking about this process, he uses this language of "descent" and "ascent" frequently:
"no one should deny the danger of the descent ... every descent is followed by an ascent..."
More generally, shadows are symbolic of any sort of negative experience through which one has to struggle. You might hear someone talk about "struggling through the shadow of depression", for example. It's a bit of a poetic device, but it's quite common.
Where, in your translation, is the preposition per , which means "through" ?
In your translation, it looks as though "the shadow" (umbram) is the direct object of "to ascend" (ascendere), which in this sentence is not correct, since the preposition per is governing umbram .