Lessatono is Kathruia's sword. She is the only one who can use it properly. It is a blade of Light.
The word is derived from the Alhari script for "Light Scimitar". Lessa, meaning Light, and tono meaning blade/sword/scimitar.
In the 3rd age, about 1000 years ago at the begining of the story, Zyaji had risen to power and was conquering the great nations all across Mystice. The white wizards were
fighting him in Hallovania(which is now Yovania and a terrifying swamp with dead cities and graves), this left the western side of Mystice open for massive attacks. Before the Terrans colonized Nunga, it was occupied by Zyaji's forces and used as a middleground between the travel across the sea and the conquering of Tiagor and the Alhari region. As told in the book, Alhari Nights, which is an extra source of entertainment to be written by James Bryce(co-author) after the first book: Mystrian Fate is released, Zyaji's forces invade the Alhari desert and sweep through the land leaving each Alhari outpost, village, and town, in ruins. When they arrive at the last big city in the desert, Melza, the pharoh Delatep and his queen Keliqura fight off the invading forces. Delatep dies, but queen Keliqura lives on, using the power of her holy scimitar, Lessatono to drive out the darkness. It is a success, in a last ditch effort, she creates a giant Light storm, destroying the invading forces. She dies afterwards, and the people mummified them and put them in the Alhari pyramid with all their treasure and blades. It is believed that Kathruia is the descendant of Keliqura.