Nah, I always imagined the changeling hive to be a living structure. I had this idea that, since changelings seem to glue the ponies and other creatures they catch to the walls, after they're done feeding off of them, the still somewhat alive remnants are left to be slowly absorbed by the walls. (think pirates of the carribbean) What is left of the minds of the absorbed ponies over time became a single entity, not really cognizant but aware. Influenced by the hive mind and need to protect this entity keeps a watchful eye on it's inhabitants (hence the eyes) and even defends it if in danger (hence the fangs).Or, y'know, magic *vague hand gesture*That's just my opinion, it's really up to the person looking at it.Could be walls, could be an eldritch horror, whatever suits your interpretation.