His eyes glow when the spell activates. So....when he feels intense emotions, the spell suppresses those emotions. That's so sad.
No, regarding his cold demeanor, it's not a spell. Varkas is deeply traumatized from his childhood training. His father + the church.
Varkas can barely show any emotion because he was raised under rigorous, abusive training by his father to mold him into the perfect, unyielding heir. Someone who exists solely for duty and honor. Showing weakness, pain or emotional vulnerability was literally beaten out of him. He adopted emotional detachment purely as a survival mechanism.
I'm younger than you.......damnnnnnnnnn