Kain Darkwind's Savage Tide
Ysdon was a sage encountered by the Steel Wyverns in Ossington and a companion of Tully, Henwen and The Cuckoo. The sage was once active as an adventurer (apprentice) before retiring and settling down to pursue a more scholarly career. The height of his activity was around twenty years ago, with a group that did not include Tully. The group was well known for fighting the bullywug menace.
According to their account, Ysdon inherited his tower from his former mentor, Olwain the Fire Warden, and had struggled to protect the village against the depredations of the fae and The Horseman. However, it was later revealed that Ysdon had plotted to murder the Horseman and steal The Jade Serpent, likely after being corrupted by Henwen, and that his true nature was that of a sorcerer with infernal powers.
Ysdon was overcome by the Steel Wyverns in a battle within his tower and, though he attempted to lie his way out of captivity with the aid of the same grafted tongue that had aided his earlier deceptions, he was foiled for the final time by the Horseman.