Nightbane

Nightbane, known before as "Vampire y Nos" (welsh for "Slayer of the Night"), is a sentient cursed sword and one of the main protagonists of Midnight Soldiers: Darkstalkers' Return.

Origins
Nightbane, formerly known as "Vampire y Nos", was once a Scottish claymore forged for a welsh knight known throughout Europe as the Undying Knight, who got his name from surviving every battle he participated in without getting hurt even once. The Undying Knight, named Sir Neirin, had used the sword to fight in countless wars. Eventually, the blood of several humans spilled by the sword eventually gained the attention of a demon who tried to trick the knight into forsaking his blade. The knight was no fool, however, and he slew the demon with his sword while it was drenched in holy water. The demon's unique blood, combined with the holy water, created an entirely new creature altogether. The sword had come to life. Sir Neirin, unable to resist the urge to kill, looked for more wars to fight in now that the sword was influencing his choices. The Undying Knight soon became known as the Midnight Soldier, and his killing spree would be made infamous forevermore.