What is the RotS Yuuzhan Vong quote?

Question

I’ve seen it be referenced several times on this website, and despite reading my copy of Revenge of the Sith, couldn’t find it.

Edit: My copy of the book is Scholastic, written by Patricia C. Wrede “based on the story and screenplay by George Lucas” (front cover). It has a couple of color pictures from the movie in the middle of it.

Answer 1

Based on Valorum's updated answer on Is the Star Wars Universe just one galaxy?, this seems to have started with a Wookieepedia editor conflating the Revenge of the Sith novelization with Revenge of the Sith: Incredible Cross-Sections. The reprint in the Complete Cross-Sections book has the following:

The Imperial Starfleet will justify its existence in unending war against Separatist holdouts, dissident rebels and even, it is rumored, deterring barbarian invaders from outside the galaxy.

_{Source: Star Wars: Complete Cross-Sections (2007), page 75 (Star Destroyer—Venator Class); emphasis added}

While this is apparently a reference to the Yuuzhan Vong, all this confirms in Legends is that a rumor existed that the Empire could cite the threat of extragalactic invaders as a reason for amassing a larger navy.

Note that this reference was edited out in the Canon reprint of the same cross-section:

The Imperial Navy will justify its existence in unending war against Separatist holdouts and dissident rebels.

_{Source: Star Wars: Complete Vehicles (2020), page 78 (Venator-Class Star Destroyer)}