Shell

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A shell is a type of system member through which all other members act, front, and (possibly) blend. Shells may never leave the front. They have been compared to windows or doors, a piece of clothing the other system members wear, a conduit, or a mold other system members slot into. They can serve multiple different purposes, but many revolve around masking things such as amnesia barriers or differences between system members.

Occasionally, there may be more than one shell, who each serve different purposes.

History
This term has been used in several contexts, though pinpointing its origin or exact uses is difficult. The term does pop up in more psychiatric perspectives, but reference trails tend to go in circles, lead back to a handful of sources that are either in some ways problematic or contested, or have lacking or even inaccurate definitions of collateral terms.

Most places point to Allison Miller's book Healing the Unimaginable as a main source on shells, but she is is in turn quoting very unreliable source. Additionally, the most accessible source, the "Types of Alters" list on the traumadissociation website, is inaccurate in some of its definitions. Therefore, it is difficult to come to any definite conclusions.

However, shells are most commonly associated with OSDD-1a and specific trauma histories.

Related Terms
In partitionary systems specifically, a member like this may be called a prism.

Systems with a shell may consider themselves monoconscious, hydraconscious, or cephaconscious and may have atrial memory management.

Shells are often used to described members in orbital or non-switching systems, in this context it may be similar to a core, masker, or blanket self. A shell may be frontstuck or even a part of front and serve as a sort of "interface" with the outer world. Shells may be a form of ANP.