Saruin

Saruin is a God from Romancing Saga: Minstrel Song and Romancing SaGa.

He is the brother of Death and Schirach. Saruin Is sealed by the Fatestones in Quietus, which lies beneath the Isthmus. Saruin and his siblings sought to conquer the world of Mardias.

Saruin is one of the most powerful Gods; he created many beings to aid him in the destruction of the world and Elore. He created many powerful monsters, the most notable were the Four Elemental Lords whose powers rival those of the Gods. His first creation was Pyrix, lord of flame, Adyllis, ruler of earth, Strom, serpent of water and Avi, master of wind. He was betrayed by the Four Elemental Lords as they refuse to aid him in his cause.

He then created a Fatestone and placed it inside another of his creation, Jewel Beast. The beast consumed the Fatestone, went mad and attacked, seriously wounding Saruin in the process. He then sealed Jewel Beast in the region of Frontier. Afterwards, Saruin created his most dangerous monster, Soulgutter; an undead monster with no soul that consumes the souls of all living things. Death could not allow his brother's creation to defile the souls of the living. Because Soulgutter had no soul, it could not be killed, only sealed. Death gave the mortals a Rite to seal the creature with the aid of the Giants an Altar was created to contain Soulgutter on the Steppes of Galessa. Unsucessful with all his former creations, Saruin then created an army of lizards that he brought up from the ground: the Gecklings, which he taught to walk upright and how to fight, aided him in the fight against the other Gods. He fought Mirsa, but was sealed by the Fatestone that Elore gave to Mirsa and his companions.

Ultimate Boss
The player (after beating the game once at least), can offer up FateStones on the alter in Quietus to make Saruin stronger. With enough Fatestones, he becomes the strongest boss in the whole game.

9 Fatestone Saruin: Part 1, Part 2, Part 3.

10 Fatestone Saruin: Part 1, Part 2.