The concept of clones or copies being made to replace original people, usually either as a means of Teleportation (by creating a copy somewhere else and destroying the original) or as a way of obtaining Immortality (creating clones to replace a dying or dead original, for example). If the Twinmaker is kept a secret, it will probably be part of The Reveal. Particularly devious characters may exploit the Twinmaker for their own ends, perhaps to create decoys to lure out assassins, or to dispose of an Unwitting Pawn by "tweaking" it mid-way through its creation. Examples: