ok so im rereading GtN for the first time post-Nona, and i just noticed:

Gideon unsheathed and examined the sword. Long, black pieces of crooked metal formed a decaying basket hilt. terrifically worn black pommel seal depicting the tomb wrapped in chains, the sign of the ninth. the blade itself was notched and cracked. "only way this kills someone is with lockjaw'" she said. "How are you going to get Ortus back anyway"?ALT

From GtN, page 50. I never noticed this before. and then:

a black image of a rock wrapped in chains with a small skull on topALT

THIS, the new seal from the various nona chapter headings. which i always assumed was the sign of the tomb specifically, or Alecto, but also sounds exactly like the symbol Gideon describes as the sign of the Ninth.

because i always assumed the jawless skull with the IX on the forehead was the sign of the Ninth!! even though it was literally spelled it out for us in book 1. i just always assumed. anyway. what does this mean.