THE DRAGON PRINCE ANALYSIS!!!
Here, Viren is speaking to the mirror, saying that he thought it was going to be “something valuable, something important”. This is almost identical to what Harrow says about Viren before he died (kind of).
Harrow states how Viren feels as though he is “above the people of [the] kingdom”, specifically more important than everyone else. Viren denies this, yet uses the privilege he has as the head advisor and mage of the kingdom to steal, threaten death, torture prisoners like Runaan and Gren, and influence Soren and Claudia to do the same.
Later on, in season four or five I believe, Viren goes into his deep sleep after using Dark Magic for the first time in two years after his death. When met with moments of deep weakness, like a dying child Soren, he feels weak and useless. Dark Magic helps Viren feel powerful and important, but at the cost of his own sanity. His past self tells him that he can choose a different path entirely instead of Dark Magic, and so he does.
Idk how much of this is accurate as I am only in season two in my rewatch, but feel free to add anything and make corrections!