Even snakes are bizarre. We have a creature with no limbs, just a very dangerous head and a potentially very dangerous body, and it uses its skin to move. And they can eat things whole which are several times the size of their head. Seriously, wtf.
Oh and even better, they range in size from adorable little worms to big enough to eat a human whole. And what kind of exercise do constrictors even do to get strong enough to suffocate something that outweighs it??
Oh, how about those furless apes? I heard their offsprings have to be supervised ALL THE TIME for several years or they might kill themselves by accident. Crazy!
Because up to that point animal life was closer to sponges than anything else. Maybe a moving blob here and there in the ediacaran. Then shit evolved predation, mobility, pursuit sensation… And so what does the blob do? The simplest thing that by chance can change in its dna. And what is that? Hardened spikes with no real anchoring or repurposing. Just swords sticking out of a brain.
Meanwhile someone else is evolving to float around and have the majority of its body mass by stingers and someone else is becoming all of bugs
I'll give you a starting place. Consider their mobility, camoflauge, protection, abilities of their predators, habits of their prey, and mating strategies.
These just look like normal deep sea creatures. Ever see those videos with the marine biologists talking while they explore the deep with an unmanned submarine? They find weird shit like this all the time.