Shadowdweller
Explorer
As has been said before, make sure he doesn't fight them all at once or all together. Set up Alarm spells throughout his lair, or use watch beasts whose main purpose is to alert him when and where danger approaches.
Use traps and spells to divide the party. If the necromancer can fight them in a long, narrow corridor, have him use something like Wall of Force or Prismatic Wall to cut off the first one or two party members. Have him finish these off while the others are blocked. Use minions to delay the party while he readies his attacks.
Use traps and spells to divide the party. If the necromancer can fight them in a long, narrow corridor, have him use something like Wall of Force or Prismatic Wall to cut off the first one or two party members. Have him finish these off while the others are blocked. Use minions to delay the party while he readies his attacks.