To give Draconyx the quick and lethal appearance I looked mainly at greyhounds but also at predators such as cheetahs which all have builds that enable tham to run at great speeds. Below are some quick studies of a whippet (essentially a small greyhound)
Some images of cheetahs and greyhounds in various positions.
Because Draconyx is a swamp dweller and somewhat amphibious, I wanted to suggest that with some amphibian traits so I looked at frogs and toads for inspiration. An obvious trait to transfer onto Draconyx was the back legs which are incredibly powerful and can launch a frog or a toad a considerable distance. Another trait that I used was the smooth skin that is particular to frogs and newts (toads have bumps on their skin that contain a mild poison and, considering that Draconyx already has venom in its fangs, I didn’t see much point in giving it poisonous skin as well.).