Weapon: Anguish and Sorrow
The orc warlock Gul'dan had these daggers made for his personal assassin, Garona. The blades are said to drink blood and inflict traceless poison, leaving little sign of their grim work: the perfect tools for an assassin. She used them to carry out countless atrocities while under Gul'dan's control, including the murder of Stormwind's King Llane, whom she had befriended. Afterwards, in anguish, she asked a trusted ally, Meryl Winterstorm, to help her hide the blades away in the hope that they'd never have to be used again.
Weapon: The Dreadblades (Fate and Fortune)
Shortly after the Cataclysm, Admiral Eliza Goreblade discovered a pair of ornately crafted cutlasses inside a recently unearthed wreck not far from Booty Bay. Though the origins of the blades are unclear, their power was not, as Eliza quickly made her name known pillaging countless ships across the Great Sea, none able to best her in combat. Rumors spread among pirates and sailors about the Dreadblades, the most common ones all agreeing that they are cursed, and that if they should ever stop being fed new victims, they'll claim their owner instead.
Weapon: Fangs of the Devourer
Goremaw the Devourer, Sargeras' personal hound, claimed countless lives before it was eventually ambushed and killed on another world long ago. Following the hound's death, Mephistroph had its fangs crafted into two powerful daggers that still carried with them some of the potent withering essence that made Goremaw's bites so deadly. These daggers were passed to Akaari, one of Sargeras' most deadly assassins, who wields them to this day.