Oh I see, he's a bogeyman
You all sincerely missed him, however he's a demon and he can't appear here, so that sincerity created another unown.
But after calling him for about 50 times, your hearts started filling with anger, "Why won't he answer!? WHY!?". This anger is directed at the still forming unown, causing him to be filled with dark emotions, and there he is - a bogeyman.