please help friends I can`t beat undead

[Sharog]

Actually u can use ranged unit just fine, i went with shaman, hunter, royal thorn, griffin and arch mage.

Tactic:
#1 tower up behind the barricade with griffin on the otherside.
#2 send in griffin in front line to soak dmg.
#3, box urself up with summoned plants and totem (u probably need to wipe out some bone dragon in order to complete the build in)
#4, upkeep the griffin tank with mana spring and other necessary buffs (like the archmage shield)
#5, all range unit kill the crystal first (toke me about 4-5 turns)
#6, use time back / sacrifise to replenish the griffin stack.
#7, camp till crystal is destroyed + karador out of mana
#8, weaken the ranged unit after crystal is dead and when karador run out of mana u can then kill off the necro and the rest.

with this tactic u only take direct dmg from necro/archer and 3 random enemy melee + 1-2 bone dragon stack dmg.

with some luck u wont get a darkknight stack on u since they have so poor initiative.

Although in my game i do have the -30% griffin leadership requirement item.
combined with -50% from archmage shield and other buffs it can take quite some punishment and dish out alot of retaliation attacks.