G'valchir is a Mahakaman rune sihill that is given to Geralt by the dentist as reward for the Won't Hurt a Bit quest, or by the Royal huntsman as a possible reward (the other possible reward being the Moon Blade) for killing all ten trophy monsters in Chapter V. It is used primarily against humans and has little effect on monsters.
It can also be obtained by completing the Mud and Velvet quest and keeping the money for yourself (if so, you have to kill Captain Jean-Pierre for it). It can also be found on the Fields in Chapter IV, however only in the original version (1.0) of the game.
Described by Zahin Schmartz as "slicing up humans nicely".
It is the highest damage steel sword in the game, the equivalent silver sword being the Moonblade.
G'valchir can be imported from a saved The Witcher game into The Witcher 2. Prior to patch 1.2, there was a bug that prevented importing this sword to The Witcher 2: Assassins of Kings, but it could still be obtained via xml editing.
Mahakaman rune sihil stats as imported intoThe Witcher 2: Assassins of Kings.