If you can't pass the ambush trap, it's pribably because you have not enough death resistence or either you are still too weak to face them, I would recomend getting Hirge as a compaion because she will heal you, also, it's recomended that you wear weapon that does aditional damage to deads and ghosts, so it will be different for each ckass, if you have warrior try having area damage attack skills, if you have mage, the best is having either a summoned creature to fight for you or even the best, the mage shield+mage barrier, if having rogue, it will need evasion lvl 3, assassinate and stab lvl 3, if cleric, healing lvl 3 and skills that do damage to undead are awesome, so wear armor that gives death resistence, use weapons that deal spiritual damage or generally shock, cold, or fire could work on them too, also dont forget to use lots of health and mana potions to heal yourself or Hirge