Sync is the fifth replica of Fon Master Ion. (He is the replica before the current Ion)
Initially, seven replicas were made with the consent of the original Ion, who had been dying of an unknown disease, and authorization of Van. However, Sync, Florian, and the replica referred to as, "Ion," were the only three surviving replicas. The seventh replica, called "Ion", possessed capabilities closest to the original Fon Master Ion.
The rest of the replicas were sent to Mt. Zaleho to be thrown to the magma, but he managed to escape, a testament to how brilliant a strategist he is, being able to think of an escape plan after just being born. After his escape, he joined Van in his plot to overturn the Score, training vigorously to earn the rank of God-General. Still, Sync later declares his hate for Van, since he still lives only at Van's behest even after he is brought back into life a second time by Van himself inside the planet's core using Lorelei's trapped power.
Sync hates the fact that he exists as "garbage"; he feels he has no purpose for living and is only an empty vessel for Van's will, and blames the Score for causing him to be "stuck with this pathetic life." He uses his resemblance to Ion in order to unnerve the party, particularly Anise, who felt responsible for Ion's eventual demise, and even can speak in Ion's voice.
He dies on Eldrant after battling Luke and his companions one last time, with Anise recoiling in pity afterward at seeing a duplicate of Ion actually being so twisted and cruel.