Animated movie made before 1999
I remember watching this specific animated movie nearly 10 years ago (more specifically 1999)
The movie was about a boy who mysteriously got into some parallel universe of sorts. (kinda like Alice in wonderland)
In that parallel universe he gets to a city, where the mayor (or king I don't remember specifically) gives him a key to all doors in the whole city. But the mayor tells him not to open a specific door down in a basement. (maybe the castle's basement) BUT. The boy is tempted by someone to open that door and does it. When he opens the door, darkness comes out and absorbs the mayor (I think) and the boy must go down into the darkness and retrieve the mayor.
This is what I remember from the movie. I hope that anyone can help me finding the movie, so that I maybe can watch it again :D
Thanks in advance
