As for the Halloween update, Persson says it will include six new block types, five of which have "unique abilities." There will also be a new monster, "a new dimension" and portals. Persson explained later in a tweet that these portals will eventually be able to link between different Minecraft servers, though this functionality won't be implemented anytime soon.
So, can monsters use portals? If so, we totally would not build a transdimensional monster funnel leading directly inside of another player's meticulously crafted fortress. So, feel free to invite us to a game and leave us alone in the back room for a few minutes ... okay?