A: Cult Mentality, +1 Charming Sociopath, Recruit
B: +1 Cult Lieutenant
C: +1 Cult Lieutenant
D: Secret Sadistic Ritual
The Cult has a shared HP pool just like a normal character. 1 point of damage causes a single cultist to die. Area of effect attacks and traps only affect them once. Single-target Save or Die effects instead cause the Cult to lose 1 HP. Other single-target spells effect the whole Cult.
It takes a certain charismatic insane individual to run a cult, and that person takes the form of the Charming Sociopath.
The Charming Sociopath is the de facto leader of the cult, and his presence is required when the cult attempts to recruit new members because—and let's be honest—this whole cult thing hinges on his charisma.
The Charming Sociopath is a level 1 Cleric, but otherwise functions identically to a Cult Lieutenant (see below).
If the cult should perish, none but the Charming Sociopath survive. Then if he survives the adventure he may return to town and recruit d20 gullible cultists.
Once per week, the Charming Sociopath can climb up on his soap box and spew his ideological vitriol to the masses. This requires a Charisma Save, and if successful The Cult recruits d6 members and gains the same amount of hit points.
Lieutenants are named characters that hold more sway in the cult than its lesser members, but not as much as the Charming Sociopath obviously.
Once per encounter, a Cult Lieutenant can act independently of the cult.
Secret Sadistic Ritual
Once per day the cult may convene in a secret area and enact a secret sadistic ritual. During this ritual the Charming Sociopath can sacrifice up to d6 members of the cult. The Cult loses the same amount of HP permanently. For every member sacrificed, the Charming Sociopath's gains +1 Casting Die and +2 Spells until dawn the next day.