Protector

Protectors are enemies found in the Promenade of the Condemned, Graveyard, and Slumbering Sanctuary. They do nothing on their own, but protect enemies around it.

Behavior
Protectors don't move, can't be aggroed, and can't attack. The only thing they can do is give nearby enemies force fields, making the invulnerable.

Strategy
Protectors are extremely high-priority targets. While they are active, it becomes extremely difficult to fight anything else nearby. While their force fields don't have a 100% uptime, the time frame of vulnerability is small, often not enough to kill an enemy before it goes back up again.

While the Protector is generating the force fields, there is a lightning effect between it and the enemies. Pay close attention to where it's coming from to find the Protector.

You can lure enemies outside of the Protector's range to disable their force fields. This strategy is especially important against larger enemy packs in higher difficulties where enemies can chase you if you try to rush in to kill the Protector.

Trivia

 * This enemy used to be named Defender.
 * Interestingly, Defenders are enemies carrying Protectors in the Astrolab. They are like mobile protectors.
 * The character design is a clear reference to the training dummy from the first area of every run in Rogue Legacy.