Besieging undead armies

[Mightypeon]

It may perhaps be worth it for Rose Ulm, who have a handy onbattle caster of solar brilliance, and whose troops have MR14 base with an easily accessable antimagic boost, combined with not having very good amounts of banishment.
Although for Ulm, Iron Blizzard tends to kill more undead than banhisment, and does not care about MR.