so the reason tetraspaces adopt human forms is to communicate with humans. "their" "goal" is to find the strongest million or so humans, implant them with tetraspace eggs, they fight to the death, the ~1% who survive get to be the new tetraspaces, repeat
of the remainder,
some just don't get humans quite right. facial features are off, "close enough" by their standards but not by ours. arms and fingers the wrong length. garments don't actually make sense as clothes if you pay attention.