Summoning Monsters

A long time ago, probably in the 90's, I played a MOD for Doom which granted the player to summon monsters into his own army and use them to fight the enemy.

You had a manapool, which was your resource with which to summon the monsters. Your mana was regenerated by mana fields (for lack of a better description). Essentially, the wad specified a specific thing number and that thing became a mana pool that would give the player mana when run over, and then it would regenerate it's mana slowly over time.

Me and my friend would make primitive, but vast, castle maps where we would each have a base (essentially just an enclosed area) where we'd have a big ass mana field. In between the two bases was a constant battle between our two monster armies. It was a blast, I tell you... Had lots of fun with that.

Anyone know the name of the mod? I'd like to try it again.

Was it ZDoom Wars by any chance?

If it were in the "probably 90s", it was more probably Doom Wars, which was the inspiration for ZDoom Wars.