Unsent of Final Fantasy X

Apparently any humanoid with very intense emotions can manage to stay behind in Spira in a shadow form that is called "unsent". Unlike ghosts, most unsent are virtually indistinguishable from live humanoids, although it is said that the Guado can sense a different kind of scent emanating from unsent beings. Examples of unsent characters on FFX and FFX2 are: Maechem, Auron, Yunalesca, Mika, Shuyin, Lenne, Seymour...



Recently Departed
It appears that the "regular unsent" has only the same powers all Spira's humanoids have, for instance, Mika and Auron seen to need to use chocobos, shoopufs and ships for transportation and can not cross locked doors. This may be due to the fact that Auron and Mika have just joined the ranks of unsent, after a fairly recent death 10-20 years ago

Unsent Mages
Unsents that have some kind of magic training can have additional powers above what a regular person in Spira has, i.e. Maechen, a Black Mage, can appear all around Spira at his will, managing to get into locked places such as the Airship Celsius and Leblanc's Castle in FFX2.

Unsent Summoners
Unsent summoners seem to have the most power and can possess a person's body(Shuyin, Lenne), appear and disappear at will and even use several kinds of powerful magical forms: Seymour can use Seymour Natus and others, Yunalesca has two forms also.