In 'The Book of the New Sun', what is the name of Severian's sword?

In “The Book of the New Sun,” Severian’s sword is named Terminus Est.

Master Palaemon gives Terminus Est to Severian when the young torturer is exiled from the Citadel and sent to serve as lictor of Thrax. It is an execution sword, designed for decapitation rather than thrusting. Severian describes it as “light to raise, weighty to descend,” a phrase that reflects both its construction and its grim purpose.

The blade contains a channel filled with hydrargyrum, or liquid mercury, which helps explain its unusual balance. It has distinct edges for executions and a square-ended design associated with swords of justice. Severian carefully cleans, oils, and sharpens it, treating the weapon as both professional instrument and symbol of office.

The Latin name is commonly translated as “This is the end,” though interpretations such as “this is the limit” are also possible. Terminus Est is not merely equipment: its cross-like shape reinforces the series’ religious imagery. The sword is ultimately shattered in Severian’s battle with Baldanders.