Shalla'tor was one of two magic elven blades (the others being Ellemayne) forged during the War of the Ancients and wielded by the twins Vor'Illian and Lo'Vellian. They eventually came into the possession of Lady Jaina Proudmoore, who gifted them to the two personas of Varian Wrynn, who had been separated by Onyxia's magic.
In Darnassian, Shalla'tor means Shadow Render.
When the two Varians became one again, Shalla'tor and Ellemayne were fused into a single weapon. This sword became known as Shalamayne.
The two Varians, wielding Ellemayne and Shalla'tor
The combined sword Shalamayne