A lightsaber was created and wielded by a member within the Jedi Order, an individual who shared a long-standing friendship with the Jedi, Dooku. Following the demise of the lightsaber's original owner, it ultimately came into Dooku's possession. Dooku then presented it as a gift to the combatant Grievous, marking the beginning of the would-be Jedi killer's collection.
Once upon a time, a Jedi, specifically a member affiliated with the Jedi Order and a former companion of Dooku - also known as the Count of Serenno, a one-time Jedi Master who transitioned into a Sith Lord and became the figurehead of the Separatists - personally crafted and utilized their own lightsaber.
Subsequent to their passing, the lightsaber ended up in Dooku's hands. Later, Dooku bestowed it upon the Kaleesh cyborg General Grievous soon after saving his life after the shuttle incident that Dooku secretly planned. Grievous was then named Supreme Martial Commander of the Separatist Droid Armies and evolved into a notorious Jedi hunter, expanding his arsenal with the saber and Dooku's tutelage.
The initial mention in canon of Grievous' inaugural lightsaber appeared within the "Helmets" section of the eighth edition of the magazine titled Star Wars Helmet Collection. Within the context of Star Wars Legends, General Grievous' first lightsaber originally belonged to the Jedi Master known as Sifo-Dyas, and it featured in the Star Wars: Visionaries comic strip entitled The Eyes of Revolution, which was released on March 16, 2005.