Severus is a bitter dragon. As a hatchling he had to watch the way his rather arrogant father treated his devoted mother and this has left him with contempt for both of them. With his father for being so self-obsessed and his mother for being so weak and letting his father treat her that way. Although he has inherited both of their good traits - like his father's courage and his mother's work-ethics, his bitterness has left him lonely among his fellow students.
While Severus' intellect has gained him the respect of at least a few magis at the academy, he has no real friends and the hatchlings and younger students all fear his impatience and foul mood.
Even his mating to Sethra leaves him unfulfilled - it's more a thing of convenience than love.
You have a sentence fragment, herk! (The bolded bit)
Also, a comma is needed after ethics and after academy, and an apostrophe after Severus (all bolded for you!).
In English, it's usually foul moods, rather than mood.
Nice description, though!