By the way, the Necromancer has a morale compensation: when taking the Skull of Markel and the Flesh Tunic, he doesn't receive penalties (if all troops are undead).
Besides the Necromancer's amulet, you can also remember the rune for the Dwarf, which gives only 1 SP, but costs as much as 6500. It makes sense to add more spells for a higher price to reduce the specific cost of SP for other races, based on this artifact.