Elude Undead
Servants of Darkness, Powers of Undeath, bow and be humbled by the blackness of my soul.
This spell fills the necromancer with the energies of Undeath, making any Undead ignore him.
Intelligent Undead will see the caster as one of them, but they are free to ignore or interact with the Necromancer as they see fit.
Note: At character creation, this spell must be chosen before any other spell of it's level can be added to your book. In instances where multiple spells like this are available, only one needs to be chosen.