Bloodvein, a Vampire dragon controlled by Pinkieseb, was Branwen's personal guard and friend before he was fired. His loyalty has changed drastically since then, as he plots to kill and steal from Branwen.
Bloodvein can be considered quite aggressive. He is destructive and mean to everyone around him. At the end of the day, Bloodvein is loyal to himself and no one else. His ignorance and arrogance can often get him in trouble. He isn't the smartest when it comes to important decisions and often chooses to run away from problems then actually solving them.
Taken from Bloodvein's character sheet:
"Bloodvein used to be a nebula once, but when his family was killed in the war a group of vampire dragons attacked him. One of them bit into him and then they walked off. Leaving him soaked in blood and surely going to die. Surprisingly as the next day's sun rose up he could stand. He looked at himself and realized he was a Vampire dragon. He licked the blood of himself and loved it, he ran out and went to find some more. He came into the Kingdom of Night's territory and was attacked. He surrendered and was taken to the Queen, after a bit of talking they became allies, from there they became friends and he became her personal guard by request. He never did find out how the vampire dragons got here, but that is just another mystery to solve."