Infernal protectors, often called "IPs," are found only in hell biomes, where they stand guard over various bunkers and dungeons, radiating a purple glow and causing severe damage to any player who strays inside their ranges.
Infernal protectors cover a radius of 20 blocks, but the purple glow is visible from up to about 75 blocks away.
Each hell world has 12 infernal protectors. You can't destroy an infernal protector in the usual way, by mining it -- you must first repair the expiator, and then bring ghosts to the expiator to release them. Each released ghost will remove the infernal protector from one random location in the world.
How to Obtain
This item cannot be obtained into player inventory.
How to Use
For more information on how to destroy infernal protectors, see the expiator page.
At the time of this writing (March 2016), PC users (and others using v3) are unable to see the purple glow of infernal protectors.