It's almost like having just regular civilians go into a dungeon from another world with magic and shit without any military/security or countermeasures was... fucking retarded. Imagine that.
You'd think after seeing how many people live on this world and how society is that the elf might mention, uh, I don't fucking know... A monster that can shapeshift into anything it eats. I'm sure THAT won't be a security hazard. No, sir. Not at all. Not like it's a perfect serial killer in the making. Nope. Nah.