Incident:111a (Music)

"Yeelon also ''Demon'' is a mysterious character who only appeared in Incident: 111a and not in any canon episode.
The Yeelon's mouth is a reference to "SCP-087-B". It is also rejected the concept of the Tricky and Auditor crossover in Madness Combat 11, as confirmed by Krinkels."
-Madness Combat Wikia