The Arcturian Heresy is one of my absolute favorite in-game books. I find Tiber Septim to be one of the most interesting historical characters to learn about in the Elder Scrolls. The whole air of intrigue between Septim, Arctus and Wulfharth is so deliciously deceitful, conflicting and mysterious. HOWEVER, I cannot truly call myself a scholar on the subject of the aforementioned three, as I have lived many years of having no idea what the [NUMINIT] I'm reading here. Allow me to present this quote from the Arcturian Heresy:



And another



What I understand is that this epic battle between Arctus and Wulfharth (The Underking and a Shezarrine), resulted in Arctus capturing Wulfharth's soul, as they needed some of Lorkhan's power to use the Numidium. However, the Arcturian Heresy's explanation of the battle does not shed any light on this query at the end. How is it possible that the soulgem could contain the soul of Septim or Arctus? As I understand it, after the apparent death of Arctus, the Underking reappears as an amalgam oversoul of both Zurin Arctus and King Wulfharth. And somehow after that, Tiber Septim becomes wrapped in that dual-being to form the three-headed Talos who later achieved CHIM.

Perhaps my plea is a bit disjointed. I have consulted http://imperial-library.info/content/rise-tiber-septim sources for the answer to this. But I'm just not getting it. I guess my essential questions are:

1. How could the soulgem have captured anything but Wulfharth's soul?
2. How could the mantella have contained the heart of Tiber Septim, and why would that power the Numidium?
3. How did Arctus and Wulfharth's souls somehow combine to make the Underking?
4. How did these three powerful individuals come together under one oversoul to become Talos? (I understand it has something to do with mantling and replacing Shezarr in the Cyrodiilic pantheon, but how could that ascend all three of them?)

I've been reading Elder Scrolls lore for years now, but sometimes a man just needs it handed to him. Detailed answers would be cherished and worshipped.

Tiber Septim achieved CHIM before he became the God Talos


I don't think I understand thsi question. Are you asking if it's even possible for Arctus' soul to be captured?

I think "heart" is a bit more symbolic than you realize. And Tiber Septim is technically more than one person, as you've already essentially pointed out, so there you go.

My interpretation of the relevant events: Wulfharth got epic soul-trapped; Wulfharth's heart destroyed Arctus'; this mimics Lorkhan's death enough to make Arctus come back as the Underking, "replacing" Wulfharth as the Underking; people see Arctus-Underking and think its teh same Wulfharth-Underking, similarly how they thought Hjalti-Tiber Septim was in two places at once when Wulfharth attacked Morrowind in his stead.

Warp in the West. Talos didn't exist until Morrowind.