As Utgard I say don't counter darkness, benefit from it. Utgard is well positioned to work under darkness. Depends on what specifically you're fighting in the darkness and what you've got researched, but here's some things to do in the dark:
Drain life, leech, soul slay, etc. Precision 100 spells don't care that it's dark. You've got many great options for dealing with demon/undead SCs.
Skellispam, summon imps. Throw in blood lust/rush of strength, battle fortune/will of the fates, quickening. Summon water elementals, which are hopefully ice elementals. Not too many nations can out battlefield-summon you. Better yet, forge lifelong protections and bottles of living water to stick on the guys doing the skellispam. >
Grip of winter/rigormortis/soul drain if your enemy isn't undead. Standard undead counters (Dust to dust/wither bones/undead mastery) cast by undead mages (mound fiends, liches, etc) if he is.
Demon cleansing - great way to make buffed skellispam > demons if that's what you're facing.
....ok, more specifically, looks like you're facing blindfighters and undead. That would be low level undead being skellispammed mostly, right?. Simple imps in sufficient numbers should dominate that, the blindfighters are going to tire out quickly and the undead shouldn't be able to build up critical mass with fliers pouncing turn one. Equip a few lifelong protections, have some B1 hags scripted to summon imps, reinvigoration, summon imps, reinvigoration, summon imps with a Skratti casting bloodlust every couple turns. If they're fielding tougher undead have a Gygja drop light of the northern star and have a bunch of S1 hags spam solar rays. If you're looking at larger numbers of skellispam make sure you're in a cold environment (wolven winter) and drop several ice elementals. Combo this with the imps (so the elementals don't get focussed on) and you'll squish right through almost unlimited longdead. Supplement with quickness and haste as appropriate, and etherealness/luck wouldn't hurt either.