This article is about the memory. You may be looking for the mercenary.
Atos the Beast Caller was a virtual representation of one of Kassandra's genetic memories, relived by Layla Hassan through the Portable Animus HR-8.5.
Description
Kassandra tracked down the mercenary hired to eliminate her.
Dialogue
Kassandra found the mercenary in Patrai and attacked him. She eliminated him and recovered a letter on his body.
Outcome
Kassandra eliminated Atos the Beast Caller, discovering that more mercenaries had been hired to eliminate her.