Internal Self Helper
An internal self helper is a headmate whose role is holding knowledge about the system, headmates, trauma, and/or internal workings. Some internal self helpers may also be gatekeepers. They know a lot about and can explain the inner workings of their system, whether it be to those external to the system or new headmates
Some ISH may guide individuals around headspace and potentially greets new system members. These headmates are typically called a "Ferryman".