Behemoth?

[Kobal2]

Any single target damage spell will target the Behemoths first (because of high HP and size) so early on Thunder Strike, Flame Bolts can do the trick. Later on you can count on Petrify, Disintegrate, Incinerate... Also note the Behemoths aren't Mindless like most undead (presumably because the necromancer mahout isn't) so Paralyse, Mind Hunt and Soul Slay all work, as do Charm and Enslave.

Of course, there's also the even cheaper option of massing archers or crossbows - Behemoths only have 7 protection so unless they're ethereal and you can't cast Flaming Arrows, missile fire of any kind will schwack them in short order (or cripple/limp them which is the next best thing).

I wouldn't really count on Earth Meld, Vine Arrow/Storm of Thorns or Fire Cage/Prison of Fire though: Behemoths are high strength and ridiculously high morale so at best those spells would only hold them for a turn... assuming the mage even targets them - AoE spells tend to target large concentrations first and that often means the skellispam screen. Besides if they're ethereal, one turn won't be enough for your guys to dispatch them unless you've also got a fire bless.
Crushers would be a good albeit expensive option to hold them in place however. Size 6 means they won't get flattened; mindless so the fear doesn't matter; and they've got better stats than the behemoths so they should come out on top of a trunk vs. fist contest even with minimal buffing or magic support.

[JonBrave]

Originally Posted by Kobal2

Any single target damage spell will target the Behemoths first (because of high HP and size) so early on Thunder Strike, Flame Bolts can do the trick.

Could you/someone please explain this to a newb? I thought targets (for most anything) were just chosen at random? It makes a difference if you know these spells are likely to target something useful...

[Kobal2]

Originally Posted by JonBrave

Could you/someone please explain this to a newb? I thought targets (for most anything) were just chosen at random? It makes a difference if you know these spells are likely to target something useful...

I'm a noob myself so I'm not as knowledgeable about the arcanes of the domAI as some of the gurus out there, but I believe whatever spell you cast, the AI tries to maximize the number of total HP it will affect. At least for damaging and debuffing spells - I'm still puzzled by the AI buffing priorities.

But anyway, what this means is that single target spells will prioritize big hulking monsters (because they have a lot more HP than Joe Spearman next to them) while AoE spells tend to target large masses of chaff (because each square holds 3 guys, 10HP each, hence hitting just 3 squares of Joe Spearman (90 HP total) does more damage than killing, say, the lone and almost killed Prince of Death with brand and shield who's completely ruining your stuff.

I'm not bitter.