Nah, not on the battlefield. I'm just outside Bel's hall, going to the hall of judgement to start the hunt. From what I can tell a stream of spirit warriors and spirit wolves (or whatnot) keep entering from where the Valley of Annwn enters to the halls area. This wouldn't be much of a problem, except that I don't have an infinite source of spell points.
I'm fairly sure they're constantly spawning, I'm not sure somewhere around 30 creatures could fit in the cavern I'm talking about.