I won at the first attempt, quite lucky i guess couse by accident i used quite good and effective tactic.
I would say that you need to have necromancers in your army if you got the Dark commander skill that gives +initiative to undead it helps.
When i started combat i did Fire Rain on their necromancers , im a mage so i had x2 spell in 1 turn. When i killed their necromancer i used mine to ress his and i had 2 x necromancers.
Be sure that when you kill an enemy stack next to move is 1 of your necromancers, becouse if you dont take control over the dead bodies the Boss or his crystal will ressurect them
I guess thats simply the key.
Ofcourse there is the spell of light thing that do damage and make the mobs go away but Fire rain + 30% Fire amulet if you got it is kinda better. Just eauip intel items to be sure you kill their necromancer in 1 turn so you gain control over him by ressing him using your own necro.
P.S
BTW as i remember when i won the fight there was an item that i bought in the castle (maybe it was some other place but i think it was that castle)...the item name is PAIN SKULL and it also have a 2nd lvl called DEAD SKULL, i cant simply upgrade it. There is something like: Power of Spell : 100% and im guessing from the info when i will use the item in many fights and it feed itself with my mana (steals 50% of mana every fight) the power will go to 0% and i will be able to upgrade it.
So my questions are:
1. Do it really needs to be used till 0% of power of spell when it can be upgraded?
2. What are the Stats of the DEAD SKULL? (is it even worth to try to get it)
2.I noticed that 1 fight lowered 2% of the power. Do i need to fight 50x to take it to 0%? Im a mage i cant afford that.