He still hadn't stopped running. Knox was bolting from one corridor to the next, his head spiraling with thoughts concerning his previous encounter:
'Well, that was rude.'
'How could you just run away like that?'
'Not only did you run away... You ran away FROM A HUG!'
'A hug from a beautiful mare, I might add!'
'Well, it would've been way more natural (and less panicky) if she hadn't hugged me so much like...'
"Cozy Glow?" he asked to nopony in particular as he was dragged forcefully out of his sprinting panic by a familiar rustling sound coming from behind the closed library doors.
It couldn't be her. Could it? Last he'd heard, she was still rotting away in Tartarus, for Celestia's sake! But, maybe... He hadn't read any newspapers or anything for months. He'd sort of given up on the world after the last newspaper he'd read. He knew that Cozy probably wasn't free. Yet here he was, about to open those same familiar doors with the same familiar sound coming from behind them. Come to think of it, the sound from the library seemed to be a lot louder than he remembered.
Nonetheless, this was the the moment! He was finally going to reunite with his friend! 'Maybe I won't be so broken once I see...'
Knox didn't know what he'd expected. Actually, that's a lie. He knew exactly what he'd expected. He hadn't truly expected Cozy Glow to be there. He'd only been partaking in wishful thinking. In all honesty, he expected to be disappointed when he opened that door. Inside the library flew, not a curly-haired little pegasus as he'd hoped, but instead a teenage blue griffon. It took Knox a moment to realize who exactly this griffon was: Gallus.
Gallus was one of the six creatures who saved all the magic in Equestria. It was them who had defeated his friend and destined her to be locked in Tartarus for the rest of her days. His eyes filled with hatred as he eyed the griffon.
This. Was. His. Fault.
Before he even knew what he was doing, he'd grabbed Gallus' tail telekinetically and pulled him to the floor in front of him. Hard. He exploded with a fiery rage he didn't even know he possessed.
"You did this!" he screamed at the griffon. "You took her away from me!"
The griffon was struggling, trying to get away from the pale pink magic that held his tail in place.
"What are you talking about?" the griffon begged. "What do you want from me?"
"She was thrown away like trash because of you! You just had to save that magic, didn't you?"
Knox's horn began to glow brightly with a pulsating magic.
"I would've given up all the magic in the world if it meant I wouldn't lose her, but I didn't get a choice!"
Gallus looked on in horror as magical power began to crackle around his tormentor's horn. Whatever spell the unicorn was preparing, it was a powerful one.
"Because of you six, I lost the best friend I ever had," continued Knox, beginning to sound progressively more mentally unhinged, "so let's see how your friends like it!"
He reared up on his hind legs, ready to cast the spell.
Ooh! Now I see how it is going for Knox. I'm guessing he had a very hard time making friends and/or feeling accepted as he grew up. Perhaps he was neglected by his parents and came to a point wherein he felt nobody would ever care for him. Thus the lonely job of 'night janitor' kept things easy as he didn't have to be taunted by how lonely he felt in large groups.
In any case, he needs some serious love. Or, if I am guessing the personality, the opportunity to be reunited to cozy Glow. Even if it meant being turned to stone beside her.