Vial of Denial

The Vial of Denial is a passive special item with defensive applications. It appears to be a glass vial containing a spined spirit with a stern expression, and which waves its finger in disapproval.

Abilities
It allows the Player to shroud themself in delusion, denying the existence of the enemies. When below half health, enemies will flicker in and out of view. Invisible enemies will continue what they would do if they were visible, but they and their projectiles cannot damage or debuff the Player while they are out of existence. Enemies will flicker in and out of existence more rapidly on low health.

The downside to this is that you cannot damage enemies whilst they are phased out of existence, and since they continue business as usual even when they cannot be seen, you cannot now their exact positions when they come back into reality.