Thalzar was one of a trio of wizards to escape Crandor after Elvarg laid waste to the island. He, Lozar and Melzar (of whom Melzar is the last survivor, later to be killed by the adventurer) each took a piece of the Crandor map, in the hope of preventing others from journeying there. It is assumed Thalzar died peacefully - his third of the map is found in a sealed room in the Dwarven Mine, and the Oracle is now charged with ensuring only those strong enough to defeat Elvarg are given access to Thalzar's map piece.
During the Dragon Slayer quest, players will encounter an engraving from Thalzar on the lid of the chest containing one of the map pieces. It makes brief mention of the events on Crandor and asks the player to reconsider taking the map piece within.
Here I rest the map to my beloved home. To whoever finds it, I beg of you, let it be. I was honour-bound not to destroy the map piece, but I have used all my magical skill to keep it from being recovered.
This map leads to the lair of the beast that destroyed my home, devoured my family, and burned to a cinder all that I love. But revenge would not benefit me now, and to disturb this beast is to risk bringing its wrath down upon another land.
I cannot stop you from taking this map piece now, but think on this: if you can slay the Dragon of Crandor, you are a greater hero than my land ever produced. There is no shame in backing out now.