S'ym is a fictional comic book supervillain in the Marvel Comics Universe, a demon who served as a frequent enemy and sometimes supporting character in The Uncanny X-Men and The New Mutants.
S'ym is a "tip-of-the-hat" to Cerebus the Aardvark and his creator, Dave Sim, after Sim featured Chris Claremont as villain in an early issue of Cerebus . S'ym always referred to himself in the third person (e.g. "S'ym thinks this is a bad idea"), a trait shared by Cerebus. S'ym also has the same purple-grey coloration of Cerebus, and looks vaguely like Cerebus, only taller, more muscular, and with a horn. And, of course, "S'ym" is pronounced identically to "Sim".
S'ym was a minion of Belasco when Belasco was ruler of the demonic dimension called Limbo. The X-Men were transported to Limbo via several teleportation discs. While there S'ym battled the X-Men, who were also trying to rescue their missing friend, the 7-year-old Illyana Rasputin, the younger sister of the X-Man Colossus. S'ym killed...
full article at wikipedia