The subconscious, the part of the mind that operates on its own without the consent of the main ego.
Kael was aware of his subconscious self and never really thought about it. Not just him, no one ever really thought about it.
Besides, what was the point of trying to control or fuse with the subconscious when he was weak or ordinary?
The subconscious self was responsible for many things that enabled Kael's continued existence.
Thanks to his subconscious self, he didn't need to worry about breathing, he didn't need to worry about his thermal regulation, and he didn't have to remind himself to blink because his subconscious mind would do all that for him without him having to think of it.
Some of the decisions he made were also due to his subconscious, the type of meat he preferred, the reason he felt regret for some actions, and the reason why he was constantly seeing everyone as a potential traitor.
