This is a bit of a long shot, but in case anyones knows it, I remeber playing a module where both allied NPCs and enemy “boss” NPC’s constantly spawned units that marched against one another and the players job was to kill their way to the boss enemies and take them out.
When you did more powerful bosses would start spawning harder enemies further away and you had to do this a few times before you could reach and kill the final boss.
You could also gather resources and do little quests for the friendly NPC’s which would allow them to upgrade their units and if you wern’t careful the enemy forces would overrun and kill you spawning allies.
I thought it was called something like “The battle of Forgotten Fields” or somesuch, but I can’t find it anywhere so I might be wrong about that. If anyone else every played it please speak up so i know I’m not mad.