The bat'leth is the iconic curved two-handed blade of the Klingons, said to have been first forged by Kahless the Unforgettable.
Klingon legend holds that Kahless made the first bat'leth by thrusting a lock of his hair into the lava of a volcano and plunging it into a lake, then twisting it into the shape of a blade. He used the weapon to kill the tyrant Molor, and the bat'leth became the symbol of Klingon honor.
The weapon is a long crescent with several points, held by grips along its back edge, and it requires considerable skill to wield. Klingons train with it from childhood, compete in tournaments, and still carry bat'leths aboard warships equipped with disruptors.
Worf made the bat'leth familiar to his Starfleet colleagues, using one to kill Duras after the murder of K'Ehleyr in 2367 and later teaching its use to friends on Deep Space Nine. The original bat'leth of Kahless became a sought-after relic known as the Sword of Kahless.