"The Underground"

 Spoiler

So Rigura can be entered from here?

Wonder what does some of the Rigura monsters looks like?

 Spoiler

Dark Grupin? Yes I know it looks like a Lucida minus the wings and the devil tail =)

The swimming grupin looks kinda cute I gotta admit =P

For the entrance, that's where I imagined it to be. The monsters look fine to me. =)

I've been busy lately, so sorry if I was late to reply.