After playing the new tutorial, I realized that the model of the "helix" - the strange device in the portal chamber - has actually existed in the game files for a long time.
Source:
UESP (Scroll to Original Main Quest).
Now as we see it in-game:
The "helix" was originally supposed to represent the base of the Zero Stone, the tower's crystal, much as the Crystal Tower in Summerset has Crystal-Like-Law. In datamined text, we've
long since known that the original main quest revolved around the search for the Staff of Towers, and ended with a confrontation against Abnur Tharn inside the Adamantine Tower.
I just thought that this was interesting, and people may appreciate seeing it. Blackwood has taken other ideas from cut content and brought them back to life (Gideon), and this is a good example of it. I wonder if/when we'll revisit this plot thread on Balfiera in the future?