A toxic-looking Slug monster/demon(?).
(NSFW: http://www.furaffinity.net/view/24270865/ )

~MOSTLY SQUISHY, including his horns
~Sulphur symbol on his chest
~Anything green on him glows in the dark
~Drool is numbing (also glows in the dark!)
~Both mouths have tongues and can eat
~Technically both male and female sexes, but identifies mostly as male (I didn't do a more feminine reference in body type which doesn't matter but in my nsfw version only did male parts, not female lmao)
~Quite possibly a Necromancer