hes a very big and vicious dog that has been trapped somewhere with a lot of chains around it restraining his extremely strong powers as its trying to struggle out of it his loud howls of anger echo throughout the room. His barks are also very loud and scary. You hear all this noise and search around curiously as you see that dangerous dog chained up...what will you do now?...you decide...

Vader: growls seeing a human in a way of telling you to not come near or he'll attack