In my current campaign, I’ve managed to secure myself a fairly large kingdom, with an army of over 10,000 level 10s at my disposal. This would be incredibly useful if we weren’t in a fairly epic level campaign. Our ECLs are about 48 for each of us, and there really aren’t any enemies our DM is introducing where an army this low-level army would be useful against. Enemy kingdoms' average soldiers are around the 20th to 30th level each, and the monsters themselves aren’t anything to wave a finger at either. I’d level them up, but our DM has an “XP is only earned in combat against an ACTUAL enemy” rule. (Actual enemy as in one that intends to kill them.) And I’m not sure of any means where I could provide this many enemies especially without risking them dying. He has said if there is an specified way in the book for leveling up NPCs, he’d happily put it into consideration, but I can’t find anything. Is there any way I can level them up under these circumstances? Or perhaps a different use for them? Help would be very much appreciated.
To further specify how I obtained the army and what they compose of, the army was obtained by overthrowing a corrupt tyrant and taking the throne. Also, each NPC is a pretty even split between casters and soldiers.