Isaac is the second of Sandeman's creations. He, along with his older brother Joshua, call Sandeman their "Father".
Though he is said to initially have a gentle and sweet disposition, Isaac became sad when Sandeman left. He howled and cried loudly for his "Father" to return, but the guards at Manticore became fed up with his noise and began to punish him for refusing to stop crying. To keep him quiet, they cut out Isaac's tongue, leaving him traumatized by the event and terrified at the sight of men in uniforms. As a result, he became feral and violent, and when Manticore burned down, he began attacking men in sector police attire, the sight of them making him relive the moment he was abused and believing they were going to hurt him. Joshua tried to stop him and calm him down, but when Max interfered, Isaac attacked her and Joshua was forced to kill him to save her life.
Joshua buried him outside Sandeman's house.