The Serioli were mentioned in Blood Omen. In the Underworld, Mortanius removed the assassin's sword from Kain's body, and then handed it to him. As Kain took the sword, he symbolically accepted Mortanius' offer of revenge, and became a vampire.
When Kain examined the Iron Sword later, after waking up in his mausoleum, he recognized its quality. It had been "forged by the Serioli, the legendary weapon masters of Nosgoth."
There is a popular notion amongst Legacy of Kain fans that Vorador may once have been connected to the Serioli. This is based on the Defiance revelation that Vorador was the person who originally forged the Reaver. That commission alone is enough to seal his reputation as a legendary Nosgothic swordsmith, and make him worthy of that association. Although there is currently no proof of such a connection, it does sound possible. It would be interesting to find out one way or another if Vorador's history was explored in a future game.
- [BO1] Kain (referring to the Iron Sword): "Forged by the Serioli, the legendary weapon masters of Nosgoth, this blade will serve me well, in life and beyond..."
- [DEF] Raziel (referring to the mural: The Forging Of The Reaver): "For this scene depicted the forging of the Reaver - the weapon destined to become my prison - and I recognized its maker. The years had changed him, but this was unmistakably the vampire Vorador - and in this era, he still lived."