Thea Pico

we are all familiar with how toothless prowls and stalks - his body feels completely fluid - catlike. as he approaches hiccup in the cove, he extends one leg out, cautiously, keeping his centre of mass behind him in case he needs to flee quickly. his tail whips around in one smooth motion, following through his direction of motion. he's very clearly curious, yet also apprehensive. he becomes even more catlike fighting hookfang in the kill ring, arching his spine as he guards hiccup, clawing at hookfang's face and pushing him off with his legs, trying to create as much space as possible between them. fighting the red death - toothless swoops and dives like a peregrine falcon. he follows through his shots, so he doesn't have to sacrifice speed during the dive-bombs, which is a neat detail.

gronkles on the other hand, are flying tanks. during dragon training, meatlug ploughs head first at the gang. which makes sense, given their rough, armoured exterior, built to withstand blunt force. as gronkles are built like lava spewing bludgeons, they could shake off any mallet thrown at them.

nadders hop from vantage point to vantage point, scanning the scene from above. they're agile and light on their feet - with sharp talons that that could cling onto even the narrowest of ledges. from above they have a clear view for a spine shot or a narrow beam of magnesium fire. with their large talons, they can easily swoop onto an unsuspecting sheep.

zipplebacks dart their heads forward like snakes and cobras - likely an intimidation tactic. another little detail - the distinct 'click-click' as a telltale sign the sparks will alight. (which may seem obvious but I like it and it's pretty cool)

and i think one of the most interesting ones is the monstrous nightmare. they are skittish and erratic, scurrying around faster than you can get a clear shot of them - clearly shown by hookfang as he tries to escape the Kill Ring. only when he realises the only way out is through; he stands his ground and tramples anything in his way.