I beat the thing a couple of times, but I'm still unsure about how aggro works in this game.

I mean, afaik there aren't any specific skills that say anything along the lines of "make enemies target/approach you". And for mages, summons seem to do the job for them well enough, and anything that physically removes my dudes from enemy line-of-sight seems work the way it's intended (as in "can't find target? hit the next visible dude").

Not that I really need aggro for DOS, but... just curiosity, I guess. So yeah, what causes mobs to home in on party members?