It's not granted from loyalty to Valkorion, that's just how the Knights use it. Their power comes from bargaining with the Force, giving your all to an idea.
"A man can have anything if he's willing to sacrifice everything."
“A man can have anything, if he’s willing to sacrifice.” Father’s teachings were like poison on Arcann’s tongue. His modulated voice sounded foreign.
“You have sacrificed enough,” I assured him.
“No, Thexan.” His eye met mine. “This is only the first payment. There will be more.”
Time slowed and yet the world spun around us as I felt my brother slip away from me. On Zakuul, Arcann and I had conversations without words. We moved in tandem, flowed like water with one mind and purpose. But he was different now. I could feel the rage building inside of him. A rage I did not share.
I took his metallic hand. “How much are you willing to give?”
“Everything,” Arcann said without hesitation. “Will you not do the same?”