The other dimension, what is it?

I haven't read the area boss speech, nor do I often remember things well from quest lines I did a long time ago, but wasn't pianus also banished from someplace because he ate his friend? Something stronger than him banished him here. Question is, who is stronger than pap and where do they come from? And from the sounds of it, this person/thing could be good, or it could be evil but just following the laws of his/her/it's land.

I think it would be cool if when you went over there, the monsters were nice and the people were enemies. It could make sense. What if all the monsters coming over from the other dimension escaped into ours out of fear of the humans there dominating them, and are just fighting us because we look like the humans? Then, some sort of all powerful boss would be a leader of the evil human forces.