please help friends I can`t beat undead

[Ymarsakar]

A few tricks I used was to use my own necromancers to resurrect their bone dragons first. If I couldn't do that, I would step on the corpse with one of my troops and never leave.

The tanks were ancient vampires and red dragons. For the crystal, as a mage, I used a demon portal which summoned demoness, and used them to attack the crystal every round or so while the rest of my army fought off the enemy stacks.