Ocean Monument Suggestion.

add a new type of block, scattered throughout the rooms of the monument, with a switch on it.

The switch is ON by default.

When ON, this would apply mining Fatigue.  This affect is in addition to the Elder guardians.  TO be able to mine out the monument, you must not only kill the elder guardians, but you must also flip all these switches, exploring the maze of the monument.

When destroyed, they would drop blaze rods.  This would allow potions to be craftable, and also allow makign of eyes of Ender, to activate end portals.  This would make peaceful difficult more interesting.