Protector

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A protector is a headmate whose role is to protect other members of the system from external harm, traumatic memories, harmful members of the system, or other threats.

Related Terms
Nearly every system has a protector, traumagenic or otherwise. There's a large amount of subtypes too, including but not limited to: eraser, amnesian protector, avenger, janusian, warden, and swordsperson.

Persecutor and malicitor are headmates that could cause harm to the system, which a protector may be protecting against.