I am not looking for any kind of human or equivalent. They shouldn't even try since I think we agree their humanity is all but gone. The Knights have insect-like features and the back plates act the way some insects enlarge their profile in an aggressive manner. More of it would work for me. I also don't want more of the Covenant style of aggression from the past. I want to see some alien yet recognizable at the same time.

: Fluttering your back plate is no form of human emotion that I recognize. OK
: it can signify rage or anger but it's not great and the questions then
: become: why are they angry? what are they thinking? why are enslaved
: humans angry at the success of a free human? do they remember being human?
: what part of them is human?

I assume there is nothing much human about them anymore. Basically some kind of essence that acts as an AI.

: Are Crawlers actually dogs? Or are they humans? Will they yelp when scared?
: Will they feel fear? Panic? Contempt? Elation? How will they express those
: emotions? As dogs or as people?

: Will we get talking dogs or barking people?

A four legged creature can pound its fore paws on the ground, raise its back like a cat. I suppose there are a tons of aggressive behaviors that could be mimicked. Nothing human of course.