Im lazy rn, but he has 6 functional deer ears blending into his curls, though he typically folds down the other pairs for comfort. His hair is golden blonde, that transitions into orange and red at the tips of his ears. His skin is pale, though not as white as Lucifer's, with a golden permanent eyeshadow. His eyes are red with a white sclera, switching to a gold and black in his more demonic form, along with red circles on his cheeks. He's tall and veeerry sassy. He can be a bit vain and prideful with a haughty exterior, but he's actually pretty down to earth. He's a charming gentleman with a wickedly sharp tongue.
He adores his auntie Rosie and follows a bit after her, dabbling in counseling as well as the arts. He's a huge fashionista and overall designer, rivalling even Velvette's talent, and handles orders even from demonic royalty. His singing voice is also incredibly angelic. He gets orders even beyond the Pride Ring for his clothing, art, music, and even for simple advise with how charming he is, which lends him some connections even outside the ring.
His power isn't something to laugh at either, despite how dainty he presents himself. Even his voice is as angelic as it is deadly, capable of powerful attacks and spells(though he loathes using it for its hypnotic properties and the like; he isn't so uncouth and would prefer actually working to earn his influence, thank you very much.) Alastor ensured he would be able to protect himself even without his protection, and he grew to be a skilled fighter. Noble demons hire him as an escort not only for his style, but as a bodyguard as well.
Though keeping their relationship casual and even professional to the public eye, Cassius adores his mama. They have a very good relationship, Alastor not ever minding indulging Cassius' hugs and kisses; being rather physically affectionate to those who holds his favor. Cassius is pretty dismissive of Lucifer as his father. The latter was absent since his birth, and though he doesn't completely hate the man, couldn't bring himself to care for him either. The most he could feel towards him is general disapproval and frustration whenever he sees his mama reminiscing; feeling his dislike grow whenever he's given a hint of Alastor's heartbreak towards his father.
This is more a little sneak peek, and the last of my updates on any AUs for a lil bit while im focusing on academics, but I can say he's definitely going to pop up in some of my written works/AUs. Its a different AU from my Angelic Alastor one, and planning to insert it for that one ficlet i wrote.