I remember very clearly when I was first working on my own campaign I was trying to 'fill in' the troops for a border lord by rolling for followers and i was thinking about NPC fighters. Some can only go to specific levels and cannot advance any further; others can do as they like, just like PCs. And this is when Dragon mag had new character classes every month, all listed as "NPC class" [wink, wink]. But then I realized - an NPC only class or more made sense! Those are the men and women that don't have the spark, drive, or ability to be a PC. Here is an example of an NPC-only class from my campaign that will be included in my upcoming OSR supplement Far Realms.
I have not included the experience point chart or spells by level chart.
Religious Brother/Sister: While Clerics are crusading priests the majority of priests are more prayerful and contemplative. Religious monks, nuns, sisters, and local priests are more focused on the day-to-day care of the members of the religious community, prayer, and scholarly works. While most of these devoted men and women are 0-level, some few can gain greater abilities from their meditations; while these Religious Brothers (throughout this description Religious Brother is used to represent both men and women) are not suitable as player characters they are the NPCs who serve in monasteries, convents, parishes, and even as henchmen. Religious Brothers may be Humans, Half-Elves (maximum of 5th level), or Halflings (maximum of 5th level). A Religious Brother must have at least an 8 Intelligence and an 8 Wisdom. A Religious Brother with an 8 Wisdom may reach 2nd level; for each additional point of Wisdom a religious brother has a +1 to their maximum level (i.e., a Religious Brother with an 11 Wisdom can reach 5th level while a Religious Brother with a 14 Wisdom can reach 8th). Regardless of other factors no Religious Brother can exceed 14th level for any reason.
Religious Brothers may be any alignment other than True Neutral.
Religious Brothers have six-sided hit dice per level until 9th level, then add one hit point per level thereafter. Religious Brothers receive bonus hit points for exceptional constitution scores as a member of the magic-user class. Religious Brothers make saving throws as clerics of the same level. Religious Brothers fight as magic-users.
Religious Brothers may Turn Undead as a Cleric, but with less ability. At second level they Turn Undead as a 1st level Cleric. This ability improves every other level (a 4th level Religious Brothers turns undead as a 2nd level Cleric; an 11th level Religious Brother turns undead as a 5th level Cleric; etc.)
Religious Brothers use magic items as clerics, but must make a successful saving throw vs. Poison to receive ability or level improvements from magical writings. Also, they use clerical scrolls as if they were 2 levels lower. Unless over 12th level they cannot activate a Gate function from a Necklace of Prayer Beads or use/be affected by Talismans of Pure Evil/Ultimate Good.
They start play with 1d4 x 5 gold pieces.
Religious Brothers may wear leather, studded leather, scale, and chain mail and may use shields. They may be proficient in the dagger, knife, club, and quarterstaff. At first level a Religious Brother is proficient in 1 weapon and has a -5 non-weapon proficiency. Religious Brothers gain a new weapon proficiency every 5 levels.
Religious Brothers never attract followers and may only have men-at-arms, hedge wizards,and other religious brothers as henchmen.
First Level Second Level Third Level
Bless Augury Ceremony*
Ceremony* Ceremony* Create Food and Water
Create Water Chant Cure Blindness
Detect Evil Detect Life Cure Disease
Detect Magic Holy Symbol Dispel Magic
Magical Vestments Know Alignment Glyph of Warding
Protection from Evil Light Hold Person
Purify Food and Drink Slow Poison Prayer
Remove Fear Speak with Animals
Fourth Level Fifth Level Sixth Level
Ceremony* Atonement Heal
Continual Light Cure Critical Wounds Raise Dead
Detect Lie Dispel Evil Word of Recall
Neutralize Poison Exorcise
Remove Curse Restoration
Tongues Ward, Major
*the DM has details of the Ceremonies by level.