Volume 3, “The Underworld & Wilderness Adventures” has a table on page 15 with regard to the subject, entitled “Types of Guards / Retainers in Castle.” Granted, this table is for use with random wilderness encounters with castles, but for fun let’s roll on it to see what comes up.
I’m glad to see I’ll be rolling a d6 on it. First roll result = 4. “Necromancer.” This necromancer has a 50/50 chance of being hostile to the party should they pass within one hex (actual distance not directly stated) of the castle. The suggested map to use for something like this was Avalon Hill’s “Outdoor Survival” map - thanks to Thomas Denmark at Original Edition Fantasy for the best online image I could find of the map itself. Note Book 3 says that if you use this map, all of the indicated ponds you should actually assume are castles. The closest to one another I could easily see are only 3 hexes away. Sounds like it would work for my Dordogne map: a couple of pages later, scale is described: “Assume the greatest distance across each hex is 5 miles.”
The table becomes a bit more arcane at this point. I interpret it to mean that having rolled for a Necromancer to inhabit the castle, I should now roll d4 to see what special guards or retainers there are there. Result = 4 again, which indicates d12 Gargoyles.
Moving on to human guards, the rules indicate that if hostile, my Necromancer here requires a magic item from the passersby as toll, and if none are available, d4x1000 gp.
Page 16 of Book 3 indicates that in addition to men or monsters accompanying castle residents, from 3d6x10 men will be there as guards, one half of whom will be light crossbow armed and the other half of whom will be heavy foot soldiers. There’s another sentence here about the composition of such guards being mounted, but I can’t quite make sense of it. Compare these figures to the total number of 202 officers and troops in the Keep on the Borderlands.
Finally, there’s another table for the chance that a higher level MU / Fighters/ or Clerics (or MU apprentice or d6 cleric assistants) are in the castle. Should they appear, these will be from as low as 3rd to as high as 8th level.
Though I don’t think I’ll be relying too much on OD&D as inspiration for castle stocking even though we’re playing a S&W Whitebox game, it was an interesting exercise to see what Mr. Gygax might have been playing or thought reasonable back in the days of the original Grayhawk (sic) or Blackmoor campaign. I'm glad for the game spurs of random maniacs running out from the castles to engage the party in some fashion. I'm looking forward to using that in some fashion.