please help friends I can`t beat undead

[maltz]

Destroying the crystal is quite a slow process.
I think you should just focus on fighting the stacks.

Good combos are:

(1) Take heavy loss + Time Back. This is probably the best rage spell on higher difficulties.

(2) Mass Magic Shackle (lv 3 distortion). This stops the necromancers from reviving other units. Very useful.

(3) Glot's armor / Wall / Ice thorns. They are barriers to buy you a turn or two. The most basic armor and wall are the best - as they are the cheapest.

(4) Resurrect troops back. If you have emerald dragons you can easily recharge mana. Mana is the key in such a long fight.

Then it is the optimization of artifacts and units.

For example, if you get the Ring of Snake (King after upgrade), you can use Frog wife + 2 snake stacks. (Get the plain snake, not the swamp. They are poison based and don't work well on undead). The frog wife is really good as you can carry a lot of +mana artifacts. What special artifacts do you use?

I think your leadership and stats are better than my mage on impossible at this particular point in the game. So it shouldn't be a problem.