Original

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An original is the headmate that existed before anyone else. They may have split, conjured thoughtforms, accepted walk-ins, or otherwise had their system begin, but no one has existed before them.

Not every system has an original.

Related Terms
Core and original are often used interchangeably, but there is usually one original while there can be multiple cores.

Initial may be considered a synonym of original, though a system may have several initials.