If you talk with Morshu after running from the man in the basement, Morhu will say that: he is the guy who never gonnna let us down. HE IS GASTER+CHARA+DARK MORSHU+RICK ASTHLEY! CLUES:gaster:speaks in hands, chara:possess, dark moshu:speaks in hands too, Rick Asthley:NEVER GONNA GIVE YOU UP! NEVVER GONNA LET YOU DOWN!