What's so great about...

[Boron]

1. Yeah the Tactical AI is sometimes very obscure .
My main Gripe is still that if you have either Death or Air after the 5 scripted actions you get almost only Raise Skeletons , Raise Dead , Ghost Wolfes , Phantasmal Warrior and False Horror .

2. Yeah i find IDs very inferior towards good Pretenders or AQs or WQs and even to Wraith Lords and ADs . Furthermore they get Heat-Dependant Boni/Mali on Attack/Defense iirc .

Their main weakness is their lack of etheralness . So you need either a Wraith Crown or a Robe of Shadows . Both not really good Items . The Wraith Crown is very expensive and hard to forge . The Robe of Shadows is a waste of the important Armor Slot .
Without etheralness you can get wind rided and good troops , especially tramplers can kill you rather reliable .
With etheralness you have rather low Protection and it is worth nothing vs. other SCs or Nations like Caelum .

In Short : The ID is only the average warrior like a banelord . The higher level Summons like AQs or ADs are much better though .

[Saber Cherry]

Ice devils have great stats and are poweful mages, in addition to being big and dirt-cheap. They're bigger, have way more HP, much higher (natural) protection, and better stats (in every category) than Bane Lords. They are alive and thus can use regeneration, and are immune to spells that kill undeads instantly. They can self-buff with quickness, if desired, and cast falling frost. They have an additional integrated weapon (tail). They are amphibious and can lead all 3 troop types, and one of them can summon frost demons.

Ice devils - like most SCs - are virtually immune to trample, by virtue of their high defense skill. They are utterly insane, considering you get them at level 5.

Average? No. I won't claim them to be the best, but they do have exceptionally high stats and some other nice features. They outclass Bane Lords by a large margin in every way... except that there are only 7 of them. Well, and they have encumbrance, which has to be designed around, but is made up for by their immunity to anti-undead spells.

Edit: In my experience, IDs perform much better in combat than ADs. Wraith Lords are immortal, which is nice, but outside of my own dominion, I think IDs are better.

[Boron]

I forgot to mention that IDs are Demons . So you can combat them with Flamebeaus or Herald lances .
Sure Demon is better then Undead because they are not affected by Spells but those 2 Weapons are a big weakness for them .

If you have blood you can make 2 Devils with herald lance , ring of warrior + burning pearl for 1 fully equipped ID .
The Devil has also 18 att and 16 Defense , that's roughly equal to the ID .

They should kill the ID normally easily .

The AD has Fly , 100% Fire resistence and Fire magic .
So he can do Fire shield + Phönix pyre , doesn't need fire resistence and fly and has so a slight slot advantage compared to the ID . Also the AD has thnx to his Firemagic better Attack .
So in most Situations he is more useful then the ID imo .

[Oversway]

Don't those devils have like half the hp, 0 natural protection (vs 15 for ID), and ~5 less str? You are right they have better attack and also they have better precision by 2. Defense is about the same. 2 enc vs 1 for ID but not sure that matters.

Ice Devils arn't unbeatable but they aren't pushovers either.