Son of the Serpent
Pupil
You could have a dispute between the high, middle, or both ranking levels of the priestly power structure (as drow are ruled by priestesses) of the city's military and the same present in its arcane leadership which is causing a hige amount of disfunction and cloack and dagger fighting and subterfuge.
Perhaps two very prominent members (one of each) are twin sisters who are rivals in the priesthood. Both having heavily involved themselves in one or the other side of the power structure. Both with followers.
Perhaps two very prominent members (one of each) are twin sisters who are rivals in the priesthood. Both having heavily involved themselves in one or the other side of the power structure. Both with followers.