please help friends I can`t beat undead

[dukenukem]

hi everbody.King`s bounty the legend amazing game i have seen since many years.

Last day i started to play on impossible with mage.When i came to necro castle undead general was level 25 at-20,de-25,int-15 and his army strenght 130 knights,150 necros,2000 skeleton war.,1000 skeleton arc.,100+ vamphirs,150+ ghost.

My leadership was 16000,level 22 at-12,de-22,int-27 and my army 80 horseman,80 knights from demonis,700 dryads,80 shamans,70 arc mages.

may be i tried with 10 different army kind.But i could not accomplish this duty.

and my higher magic,magic power,chaos vs. was full.

Please give me some tactics to beat undead general...