Finny belongs to one of the largest species. However, it is rather rare due to it's hunting technique that depends on the prey being clueless. (Explained later)
During the day he is very active and travels a lot. His built is very light, so he doesn't need much energy to move. The little antennae give off a slight glow, only noticable in darker places like the forests he prefers to stay in. He seems somewhat carefree and enjoys most of what he sees and does a lot. He also can be a little clumsy at times.
With nightfall he undergoes drastic changes in both, size and structure.
His markings turn into sticky, sweet smelling membranes used to attract his prey (along with antennae's light), which he attacks in the blink of an eye using his long neck and sharp, beak-like snout after it entered his wide reach or stuck to the membranes.
His scales become hard enough to protect him from most attacks and their color varies between several shades of dark green and blue, making him almost appear like a group of night-blooming (membranes, antennae) plants.
The tail, too, can be used to attack. The scales along the spine end in very sharp tips, including the ones on the tail's upper side. Therefore, the swinging tail can cause severe cuts and bruises.
His weight also increases over proportionally. While his day form is unusually light, his night form in unusually heavy. This also causes him to not change location after becoming 'cruel' as long as it can be avoided.
Caused by these circumstances, he is a very patient and calm hunter. Because he does not waste energy and also doesn't loose much during the day, he can live for a rather long time without feeding on other creatures.
One big disadvantage of his way of hunting exists, though: As soon as the inhabitants of a certain area realize how he hunts and avoid him, he is no longer successful. Which is why he travels far during the day. He also needs to make sure to change in a forest, or otherwise his camouflage would fail.
... I'm sure I forgot tons of stuff, but whatever. At least I made it on time, somehow :'D
Love that world of yours, thanks for giving me the opportunity to create him <3