New Cave Feature/ Dimension

Random invisible portal in caves to alternate reality of your world. Automatically puts you in hardcore version of your world with all mobs hostile. You would have to survive and only way to escape would be to rebuild the portal back to the original world. 

Description: World would look exactly the same essentially the difficulty would be changed, and all mobs would be hostile towards player. 

Objective: Though travel to alternate reality was unplanned. Player would have to survive and gather material to return to original world (difficulty level) 

Solution: To return to original difficulty for world; player would need to recreate portal. This would be accomplished by creating a four-by-four dirt hole, surrounded by Amythest blocks, filled with water, and throwing in one emerald for lighting to strike or to be able to light by flint and steel. The player is then able to enter the portal to be randomly spawned into their world with the original settings.