S'ym the semi-aardvark-like, cigar smoking, waistcoat-wearing demon, was a long running supporting character in the X-Men, and particularly the New Mutants.
He was first Belasco's and then Illyana's chief demon enforcer in Limbo before seeking to supplant Ilyanna, thanks to Warlock's father, the Magus, infecting him with transmode virus, making him and his kind more powerful than ever.