[Lazy_Perfectionist]

Probably the Starshine Skullcap (p276).
I'm unfamiliar with Vanheim, what magic paths do you have available? And what era is this? A dwarf in support could probably get off a couple iron wills at thau3 for +4 MR. You don't need a high level spell like army of lead if you're only buffing a few supercombatants.