Quote Originally Posted by Eisi View Post
People seem to believe that

Hephaistos is part Athena for some reason - he isn't. Probably an English translation quirk.

Just because he agrees with and pursues her goals as if he were her doesn't mean there's literally a part of her soul which entered him at some point or anything like that.
People "seem to believe it" because Lahabrea outright says it, without elaborating, to the one other person who knows the full story.

LAHABREA
Athena cared naught for Erichthonios, beyond how he could serve her ends.
You claim to be acting in his interest, but 'tis plain you are no different.
As I ushered Athena to her end, I vowed that my sole mission in life would be to guide this star true.
In service to that vow, I silenced the whispers of my heart. I could not nurture a son whilst an entire world looked to me for guidance. For that choice, I bear the responsibility...
Yet he is still my son, and I'll not suffer you to seduce him with false hope. You, who are naught but the bitter dregs of Athena and I─the very worst of us!
Having tracked down that quote, I also see he alludes to having killed Athena, but that's still light on detail.