This sword acts as a +5 Longsword as well as has the below ability.
This special abliity can be activated 2 times per day, and lasts 2 minutes per class level. When the ability is activated, the Sword of Siege slices through rock and stone, literally, as a hot knife would through butter. If its point is rested on stone, it will begin to cut it, with its own weight. The Sword of Siege may be used to tunnel through stone at a rate of 30’/turn (this is assuming there is someone to remove the debris, or that the tunneler is going up, letting the debris fall below). The tunnel would be about four feet in diameter. The Sword of Siege does not have the additional +5 enhancement bonus unless fighting creatures made of stone. On a modified roll of 19 or 20, the Sword will cut off a limb or appendage, and on a natural roll of 20, it will destroy the monster.