hail,
I just took them head on. It was scary at first, but with the right defense, it wasn't that bad.
Urq (lvl 12) -- what a burden. should have let him die (and not suck up exp) than waste turns healing and protecting him
His spells were too easily resisted.
Vi (lvl 16) -- went for guardian angels, healing/stamina, and most importantly, purify air (2).
Samurai (lvl 16) -- died early on by a death cloud. resurrected near the end. was supposed to drink an Eye for an Eye early on and attack the death lords.
Ninja (lvl 15) -- woo, she's the bomb -- err, cloud. Toxic cloud (2) kept some of the cultists and elementals at bay. Since she has good artifacts and throwing, I always give her the important items. Pandemonium powder and canned elementals were used with good effect. Had purify air (1).
Ranger (lvl 16) -- acid bomb! ring of fire! smelling salts! (is there any other way to heal unconciousness?), blunderbuss! body of stone. Wasted a turn casting lvl 2 summon elemental -- the elemental took way too much spell damage.
Valkyrie (lvl 16) -- rest all, heal all, cure paralysis, purify air (3), guardian angel, occasional hit with the dread spear
Bishop (lvl 15) -- Elemental shield (7) very important, Soul Shield (5) likewise, Summon Elemental (5) very effective, Eye for an Eye, Superman (on the Greater Elementals *WEG*), Magic Screen (recast during battle just for the summons)
Bard (lvl 17) -- Heal All, Haste, Bless. Restoration potions for stamina (Ninja has 85 alchemy, lots to spare). Used Hex pipes, but it mainly only affected the enemy summons.
My party is particularly strong on defensive magic, so it was pretty much a cakewalk. Most important was keeping resistances high with the shields and screens -- even for the summoned elementals. Secondly, having multiple people with purify air to deal with the death lords' toxic and death clouds saved a lot of pain. The high level elementals competently took and dealt damage. There's nothing like a hasted, super-manned elemental hitting multiple times a round.
I'm just glad that they didn't have eye for an eye or else would have eated my own toxic clouds.