There gets to a point where the player is basically a god running around the constant flaunting their power with no real obstacles. This shouldn’t be the end. The constant should always put them through a challenge.
Planer damage is one thing but I think returning to the basics is more spiritual.
Thus I propose a special field where magic items stop working from weapons to armor. This will make players return to using a spear/hambat and wearing a log suit in order to fight always keeping them on their toes. These special reality fields could be like Wagstaff rifts perhaps by some accident from the real world which activates in hard mode and fade in and out randomly throughout the world.