Some demons breathe themselves forwards as surging tides of fog.
   Demon Lords are wary of promoting their subordinates or of progeny who grow too powerful. Most find it expedient to impress upon them that Elder Progeny is the highest station they can attain to retain a monopoly on power, and make sure that this rak is hard enough to accomplish. However once in a while through extraordinary guile circumstance and luck a progeny manages to attain some degree of power over his lord and simultaneously prevent himself from being deposed. Tales are told of rulers who have slowly become little more than figureheads because of the rise of a cunning and consummately manipulative underling. As a result demons are very cautious when dealing with powerful underlings. Yes they're very useful but they're also potentially very dangerous. The mighty owe their preeminence largely to those beneath them but the more powerful those beneath them become the more in danger they are of being overthrown. Sometimes an entire collective of progeny fall on their master. When the succeed they often set up a form of group rulership. Often this dissolves sooner or later as it's members turn on eachother. This is often the result of one of their number declaring their superiority, which often happens immediately after the coup usually by the one who slew their former master. Demons have to contend with not only their superiors and lessers but also their peers. Such an act is extremely riky as short sighted conspirators have learned. Demon Princes do not take their subsidiary souls being slain lightly and often fall on the offenders who discover they have angered a being far more powerful than the one they overthrew. Occasionaly the winner of an internecine conflict among a group of conspirators is offered the chance to be transformed into the Demon Prince's soul. Such an enticement is also used to fragment such a group of renegades, being held out as a reward for selling out their peers. Often all the usurpers perish in such a conflict which is what the Demon Prince sometimes wants.
   Having a subsidiary soul overthrown in a significant embarrassment to a Demon Prince and could incite attack from all quarters. However if one of the rebels prove to show particular promise they may think they're better off with them instead as they will be a more effective weapon to use against their rivals.