Aiden Walker is the main protagonist of the Half-Life 2: Episode Two mod Entropy: Zero and its sequel Entropy: Zero 2. He is an Overwatch Elite, but unlike an ordinary elite soldier, he has preserved his memory, his own thinking and freedom of thought. Aiden Walker comes off as a very misanthropic, no-nonsense psychopath who tends to not take many situations seriously regardless of how dangerous they are. In the Alliance, his name is simply Unit 3650.