Here are three observations, I'm not sure if they're new or not; but in case they help anyone make progress.
- Giant rune above door at start of raid: I was just in part 1 for a long time, activated it at the start, and it didn't go off the entire time (whereas the four hidden runes at the start do time-out).
- Vecna secret skulls: I hadn't really paid attention to this before; but when you successfully say a Vecna name anagram in part 1, the skull eyes light up. I'm pretty convinced that the skull eyes being lit/unlit in the final chamber are part of the puzzle.
- Kopru symbols: perhaps we have our transliterated indexing wrong and the Kopru are 0-up rather than 1-up programmers (it's a rather boring hypothesis, that five of the symbols are just the Kopru numerals 1-5):
- Our transliterated '1' (the skull/mushroom?): ? ('0'?);
- Our transliterated '2' (the eye of Vecna?) is 1 shaded circle, so perhaps '1';
- Our transliterated '3' (the eyes) is 2 circles/eyes next to each other, so perhaps '2';
- Our transliterated '4' (the triple-tail Kopru / volcano) has 3 lines/tails, so perhaps is '3';
- Our transliterated '5' (photon-photon scattering?) has 4 lines/photons, so perhaps '4';
- Our transliterated '6' (the hand of Vecna?) has 5 fingers, so perhaps '5';
- After that we have the eye/hand (which would be 1/5) in square/circle; I have no good ideas; and then of course the 'void' and '/'.