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|“||Billy, there are certain things in this world that you're happier not knowing. Even lies and deceptions can become the truth for some people of the earth... Particularly those not knowing the true nature of things, or how these systems of things works.||”|
Originally hailing from Solaris, he was once a cadet at the Jugend Military Academy in Etrenank, where he was originally known as Isaac Stein. He also attended Jugend with with Kahran Ramsus, Myyah Hawwa, Hyuga Ricdeau (Citan Uzuki), his personal rival Jesiah Black, and the love of his life, the woman who would become Racquel Black.
Stein's love for Racquel was as intense as his hatred for Jesiah, who he saw as his better and the man who he always needed to beat. Stein was passed up for opportunity after opportunity because Jesiah was always doing just a little bit better than he was. Jesiah was chosen to be an Element and Stein was passed over. Jesiah was chosen to become the commander of Gebler and Stein was passed over. Kahran Ramsus was then chosen to become the commander of Gebler when Jesiah vacated the position and again Stein was passed over. And worst of all, in Stein's mind at least, Racquel chose Jesiah over him and became his wife while Stein was simply tossed aside. Suffering rejection after rejection Stein became very bitter and vengeful at his rival Jesiah, who he saw as the cause of all his misery.
When Jesiah, now going by the assumed name of Jessie, moved down to the surface to start a family, Stein followed him looking for revenge. He joined the Solarian-run church, known as the Ethos Society, where he rapidly became a Bishop under the assumed name of Isaac Stone. He then formulated a plan to strike back at Jessie in the way that would hurt him the most: through Jessie's own family. He sent the Wels, who were produced and controlled by the Ethos, out to Jessie's house to murder Racquel, having no qualms about doing so. In his warped mind, Racquel became 'tainted' when she chose Jessie over him.
After the Wels had attacked, Stone swooped in and was the first one to befriend and console Billy Lee Black and Primera Black, the two surviving children. Using his position as a supposed man of the cloth and a trusted authority figure, he convinced Billy that Jessie was to blame for his mother's death. Billy fell for Stone's manipulation and eventually became an Etone, a member of the church who defended the people of the world against the very Wels that Stone had sent out to murder his mother.
The truth of Stone's actions only came to light four years later as darker underside of the Ethos organization was revealed. Stone ordered the death of Verlaine, Billy's friend. Once again, Billy's heart was broken upon learning that the man he had considered a father figure never actually cared for him and just used him as a tool to strike back at his father.
When Stone's treachery is revealed, Stone retreats to Solaris seeking Karellen's help. Karellen responds by surgically grafting Stone to the massive Gear known as Alkanshel, secretly stored under the Ethos HQ.
Piloting the Alkanshel, Stone confronts Billy and his new companions, but after he is defeated once, he is approached by Grahf, who offers him "the Power", which Stone accepts. In the ensuing battle, when all seems lost, Jessie appears and, using his modified Buntline Gear, he and Billy are able to destroy the Alkanshel and bring Stone to his final end.
- "Hello. Are you all happy?" (to the orphaned children)
- "Oh, Billy my son! Sorry to bother you when you're so busy."
- "Billy, my son, don't waste their good intentions."
- "I thank you deeply. Billy, take care of these people. Report back to headquarters after you get back."
- "A good-for-nothing chatterbox such as you has no right to live." (killing Verlaine)
- "The status of Bishop is merely a convenience for my activities on earth."
- "So you want to know? But can you bear the full weight of the truth? Billy, if you can bear that weight, then I'm willing to tell you."
- "I can't be bothered by insignificant wretches like you."
- "What is wrong with eliminating those not fit for salvation? Why, isn't our own very faith based on the precept that 'only the chosen will be saved'?"
- "Those who become enemies of the sacred Gazel, I will eliminate them all. Repent now."
- "Ha ha ha... A wretched son for a wretched father! Ha ha ha ha ha ha! Ha, confess to me! Pay for your sins!"
- Stone's true appearance has an uncanny resemblance to the Red Skull, archnemesis of Captain America.
- Considering the Biblical themes of the game, his name may reference Isaac.