In this mod, you would spawn and everything in the world would proceed normally. But... the only thing that's different is that something is hunting you. This "creature" spawns on a random spot in the world (not too far away) and starts walking towards you or trying to get to you slowly. Once it reaches you, it would probably cause massive destruction to everything around you and probably kill you. You can defeat it, but it would be very hard and you would need to be very prepared to do so. This would turn on a more horror-feeling while playing and some more excitement. What do you think?
I'd alter it a bit (Shouldn't destroy things, maybe a trigger for it instead of it being as soon as the world starts?) but i still really like the concept.
Kinda reminds me of the Green Demon challenge.