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His journey begun in 70 BCE, tracing down the Medjay Emsaf and his bloodline in order to eradicate them. First, he looked for him at his home, only to discover that he had already left. However, he managed to kill his wife Merti and his young son, Ebe.
However, Bion ultimately managed to outsmart Emsaf by using the corpse of a merchant he killed as a decoy, tied him to his horse with ropes. Emsaf thought his arrows had seemingly killed Bion, so he came out of his hiding spot only to be stabbed from behind by the killer, who severed his spinal column. Now only able to speak and see, Emsaf was interrogated by Bion, who wanted to know about the other Medjay. However, since the dying man would not give away any information, he swiftly executed him.
Later on, Bion arrived at Djerty, where he captures and tortures the elder Medjay Hemon and his blind ward, Sabestet. After getting the names of the last remaining Medjay true to the original bloodline, whose names are Sabu and Bayek and are currently found in the region Elephantine. Bion set his course and found Bayek and his travelling companions; however, he is caught in a trap and injured, but managed to escape. Following this event, he spends several months recovering and many years in training.
After many years, Bion encountered Aya at a watering hole not too far from where Sabu and Bayek were encamped. He helped her get away from some horse thieves and requested her scarf as a token of gratitude. Aya complied, not knowing that her presence would lead him to the Medjay's camp. Once there, Bion let loose multiple arrows that hit Sabu, with Bayek’s stomach being sliced by Bion's blade shortly after. All three were ultimately injured in the ensuing battle, with Sabu choosing to push Bayek into the nearby river to save him. In doing so, he is struck down and killed by Bion. Bayek fell unconscious and was swept away to safety by the river.
In the meantime, Aya arrived back in Siwa, where she met her ill aunt, her old friends and Ahmose, Bayek's mother. After some time, Bion arrived in Siwa too, and began to ask locals about Bayek. He also encountered Aya, with whom he had a meaningful conversation.
Eventually around 56 BCE, Bayek came home and was warned by Aya about Bion's presence. They were both led to Bayek's old home, where a fight begins. In an attempt to destabilize the last Medjay, Bion revealed Aya's pregnancy. However, Bayek didn't lower his guard and managed to defeat his opponent. Before dying, Bion revealed to them the name and whereabouts of his benefactor, Raia, who was the man behind the Medjay's eradication.