Found the text. It's not in the in-game journal, but XIVDB has his dialogue, thankfully. The relevant snippet comes after defeating the Hydra.

Quote Originally Posted by Gerolt
But what's done is done...or in this case, not done. Anyroad, let's talk about that text ye brought. It contains accounts o' the major clashes what took place durin' the War o' the Magi. The entry on the Battle o' the Gods' Grip jumped out at me. This was when the Nymians took the Amdapori host by surprise as it made its beach landin'─takin' the siege to the besiegers, as it were. As they're wont to do, the scholars played a key role in the victory, though that didn't interest me near as much as the passage what touched on the Omnilex.