Gwynian the Sage is an old sage and astronomer skilled in prophecy. He becomes a valuable friend and advisor to Lone Wolf during the course of the series. In The Lorestone of Varetta, book 11 of the novelized Lone Wolf series, Gwynian explains that he is a member of the Nameless Order, an underground alliance of intellectuals with the common purpose of overthrowing the warmongering rulers of the Stornlands countries.
Gwynian originates from Varetta, an ancient city located in the Stornlands, but he has been known to travel everywhere where his advice and presence were needed. In The Chasm of Doom he appears in a small hut near the Ruanon Pike, for instance, and in The Cauldron of Fear he has become Chief Magistrate of the city of Tahou.
Besides his talent of forseeing the future, he is also skilled in the crafting of certain magical artefacts, like the Sun Stone, which is able to collapse Shadow Gates it comes in contact with (Dawn of the Dragons and The Fall of Blood Mountain).
If Lone Wolf is arrested and fails to break out by the time of his trial, or if he breaks out only to be caught again, Gwynian as magistrate will clear him of all charges. If Lone Wolf is arrested, breaks out, and manages to get to Gallows Street to free Banedon, he'll encounter Gwynian who's already released Banedon. In either case, Gwynian will then arrange an audience for Lone Wolf in the Tahou Senate.