Highlight the white text inside the block for hints ranging from vague to specific...
"Theseus’s sudden arrival at the end is what the Greeks call a—"
Well, what is it?
Use the Greek letters (24 total) to get some English letters (26 total).
Take the position of the Greek letters from the parchment, and index into DEUSEXMACHINA (for instance, nu is the 13th Greek letter, so take the letter at position 13, which is A).
Together, these form the keyword, AXEHEADS.