Doesn't help that there aren't any walkthroughs I can find. I think I am on the second or third Empire scenario and I have a lot of trouble.
My goal was to conquer a tower (I believe an undead is loose with a scepter). I have taken all the towns, etc. except the tower (it's named Mahall). The undead in there kicks my ass and I have no idea how to defeat him. He has about 900 hp and a few helpers. He gets the first spelll off, it looks like skeleton arms rise out of the ground, and it kills my entire party. If I cast my spell that gives everybody 20% greater armor, one guy (my leader I carried over from the prior quest) survives with about 15 hp and dies in the next round. He was only able to do about 14 hp damage.
I'm playing on easy too. I have everylast bit of terrain conquered (all but 1%) and all resources. I have tried poisoning them with thiefs but it only affects the helpers, and doesn't actually kill them either.
Any suggestions would be welcome, thinking of resorting to a cheat but I hate doing that.
Thank you for the help, I was enjoying the game, but ran into a wall!

Do you have any booster potions or spells you you can cast on yourself before the battle starts? It's been my experience that you can make impossible-seeming battles easy by enhancing everyone to give 200%. With enough magic, it's possible to make a party take only 10% of all damage and put out double their maximum damage.

Thank you Prator!
I have been thinking about it. I believe this is the second scenario in the campaign, and I only have three levels of spells I can purchase, and I don't think any of them are protection spells against this undead. His name is Ashgan, in case anybody reading this remembers something about how to defeat him.
I did notice one of the parties I was fighting had a little guy boosting a troll or something in his party, but I haven't seen that I have a booster spell available.
However, I will go and check all the spells I can purchase to see if something helps. I have a lot of protection spells I could get against ice and fire and such, but I don't think that's what he is casting. I have an idea what he is casting might be some kind of death magic since this whole mission is about how he is loose with a sceptre and I have to take his Tower... I wondered if a thief could steal it from him, but my thiefs are not levelled up.
Might as well purchase any spells or potions that could help, I have maxed out the gold that you can have on this scenario (9999 gold).
I do think I remember one of the shops had a spell that protected you all day from... well, maybe some kind of death magic? That's my real hope, if that stops whatever the spell he is throwing on me right off the bat, I think one of my better parties could whittle him down if I had them as buffed as possible. Maybe that's my solution. Though, if I can't do it with one party, it will be hard because his Tower regens 35% health a day.
It seems to me t here has to be a way for me to defeat him, since I have pretty much maxed out everything on the map (I think there is only one other place I didn't clear out yet because the party of independent critters in there wiped me) though I suppose there is a risk I was supposed to level a certain kind of character to fight him.
I have also wondered if there is a way to cast some of my nicer spells I have researched on the Tower before I fight Ashgan, but have come to the conclusion that's not possible, i.e. you can't cast those spells on either a party that's in a town, or the town defense.
I'll report back once I have another go at him,for the next several hours I'll be watching some hockey (Stanley Cup ftw!).

Heh, you're trying to take on a capital guardian in a level where you're not supposed to, which is why you're getting your ass kicked (in Disciples 1 the capital guardians are basically the baddest mofos around, and even in the final scenario of each campaign taking them on is a major undertaking and purely optional). I'm guessing that your actual objective for the scenario is located somewhere else (possibly that area you mentioned where a group of monsters prevented you from exploring), so fully search the rest of the map and leave the enemy capital alone.

Darrk Phoenix - ya hit the nail on the head! Thank you for being nice about it and not making fun of my overlooking the obvious.
Let's see, I was supposed to be fighting an undead guy named x in The Tower as the objective. Instead, I was fighting the capital guardian named Ashgan.
Oh well, all's well that ends well, and I did indeed go back to the only area I hadn't cleaned out. Lo and behold, mousing over it, it said Tower and a necromancer was inside with his buddies!
I am digging this game quite a bit. I'm a sub par strategy gamer, but I can tell I am better than I used to be in that I played this game when it came out years ago and didn't get very far, but I know more about what I am doing (despite the way it must appear!).
On to Chapter 3.... and thank you both again for helping get me pointed in the right direction so I could move on.

I was pretty hard-headed myself with respect to the capital guardians. In Disciples 2 a high level party could mop the floor with a guardian pretty easily (and one campaign mission actually required destruction of the enemy capital), but in Disciples 1 the guardians were designed to be nearly invincible so complete kills of opponents weren't possible. Of course, that didn't stop me from trying various ways of taking out the guardians, most failing pretty miserably. The only case in which I was actually able to succeed was the final Empire mission (a mass-healer was pretty much essential), and that required pretty much every buff spell I could get my hands on, plus two attacks in a row because the first attack hit the 10 round time limit and triggered an automatic retreat. The first time I had tried it I'd gotten the guardian down to around 20% health, then a retreat was forced, I didn't have enough movement to attack again, and the guardian just about fully regenerated on the next turn. Now that was annoying.

I found that in both D1 and D2 there usually was one "proper" build to kill a guardian, and it involved healing \ paralysing \ high armoured units + all buffs and potions. It was much easier in D2 because of 2 things - no level cap on units and attacks that ignored armour (like freeze and poison).