Book of the Twinned Flame

When the party enters the Grand Library of the Acropolis of Kereskaa, Vichthart collects several leatherbound books from a charred, rusted and grimy chest—the only surviving contents of the Library. Among them, Mira spots one book with a red twinned flame emblem on its cover, and asks for it from Vicht, who hands it over.

After retrieving the Obsidian Claw from the Acropolis vault, the party takes a short rest to prepare for what they'll find inside the Spire of Abjuration. During this time, Mira begins to read through the book he's found. He recognizes the script but not the language, though he can read it thanks to his Eyes of the Runekeeper eldritch invocation. It seems to be a journal by a mage recounting the rumours of a conquering champion who wielded divine fire, smiting the monsters that inhabit the deserts of Calaha.

In the 3 days that follow their defeat of the bone devil, Mira spends more time reading the book. The author is a mage but isn't identified in any way. They write about the rumours of a conquering champion called The Burning Lord, who brandishes divine fire to defeat monsters across the Calaha desert. He is a local hero, with more and more people flocking to his cause, but there is no consensus on the nature of the hero's divine fire. Some rumours claim he is a mage using arcane magic, others claim he is a holy man, while still others talk about the fire being allegorical. The author is particularly interested in determining which of these is truest, and plans to journey to Calaha to meet the Burning Lord. However, the final pages do not conclude about whether this actually occurred.

Eventually someone is able to identify the language of the book for Mira. It is an old language with no particular name, used in Calaha before it died out and was replaced by modern languages that evolved from it.