It is a serpent like dragon, with no wings, which rather than fire, breathes out venom instead.
These dragons were around during the Medieval times and were said to always be in secluded places such as caves and the forests. They also always dwell in areas with small bodies of natural pools.
I guess its just searching for a good place where it could call home with clean water, a pool and is only a walking distance for food, you know, without being disturbed by humans.
If angered, of course it would fight back, I mean who wouldn’t? But there are stories that, it would run away from a human, if the human is 100% naked. Makes you think if they were scared of humans or just disgusted by humans.