Githyanki silver sword

Githyanki silver swords were weapons given to the knights and leaders of the githyanki race. They were powerful magical greatswords that came in two varieties, depending on the wielder's rank. Their most notable property was the ability to sever an individual's silver cord.

Description
Allegedly based on the Silver Sword of Gith, every githyanki 'Knight' (warrior champions in service to the Lich Queen), was given one of these weapons once they achieved a sufficient level of power to will the blades into existence. Leaders of githyanki communities carried even more powerful versions of the weapon that could cut the silver cords of those who had protected themselves from such attacks and were enchanted to increase the likelihood of decapitating an opponent.

History
Silver swords were originally designed to aid the githyanki in the fight for freedom from the mind flayers. For that reason, they were also capable of dealing damage to one's mind as well as physical damage.

No owner of a silver sword would ever willingly allow a non-githyanki to hold their weapon. If any 'greater' silver sword found its way into the hands of a non-githyanki, elite squadrons of githyanki were sent by a furious Lich Queen to take it back at any cost. If the squad sent failed to retrieve it, they would be executed.