Rythnax was a brash, boastful, and young dragon. His main joy was to tell an audience all his stories of his strength, ferocity, and cunning. However, he could attack anyone he felt had not appreciated his stories. He also grew quickly bored.
In 1489 DR, he was sent to the marsh near Phlan to act as support for Ellison Berenger. Eventually, just after Ellison joined him in his lair, the two were confronted by an adventuring party hired to recover the books that Ellison stole from Mantor's Library. Rythnax was defeated by the adventurers.