Single Line of Descent refers to the statistically improbable speculative fiction trope where there is one, and only one descendant of a famous hero or villain - preferably one who is descended through the male line so that he can inherit the name. Usually, that person has a special destiny in front of him, presumably one that ties him to his famous ancestor. Naturally, the wider the time gap between the famous ancestor and the present day, the less probable it becomes.
Game and Story Use
- This trope cries out for subversion. Make a PC believe that he truly is the last descendant of his line (bonus points if the player even wrote that into his background story in the first place) - only to reveal much later in the campaign that there is another descendant who could potentially achieve the same destiny.
- One possibility is that this other descendant becomes Evil Counterpart who needs to be overcome.
- Another is that he becomes The Rival - he might fight the same challenges as the PC, but each will try to overshadow the other in order to get the final price.
- Another subversion the PCs culture (think medieval Europe) suggests that there is only one true heir at any given time and so they are set questing for one specific bloodline. In the end, it turns out that whoever set the conditions had a more Roman or Celtic notion of heredity - any descendant will do if properly acknowledged. Rather than find the true king, they simply need to crown one.
- Conversely, if the legacy actually follows salic heredity (or something similar) for some bizarre reason there could be lots of descedants kicking about but finding the heir might be a bit trickier…
- If playing this trope straight, the most likely reason that there is only one heir left is that the BBEG has been busy killing off all the others.
- If played through the female line there could well be a significant biological - or at least biothaumaturgical - explanation for this … and tracing the heir could be a lot harder in a European style patrinomial, patrilocal society.