The Sword of the Ancestors is the strongest one handed weapon attainable in Gothic 3, with a base damage value of 120. After the blade has had the buffs of self-forged, poison, blessed, and sharpened applied it reaches its maximum damage of 150. It is also one of the few swords that offer defence statistics.
To craft the sword the knowledge of Pure Ore Forging is needed along with a Dragonroot, a Ruby Blade, and a Pure Ore Blank - along with the requirement of having the actual crafting recipe. The rarity of these ingredients makes the Bastard Sword, with the same buffs, a more viable option with its maximum damage being 120.