Here you go:
Skeletal Minion: At 1st lvl the necromancer get an undead minion (human warrior skeleton, from pg. 226 of the MM). Takes 24 hrs and costs 100 gp. As the necromancer goes up in levels, the minion gets tougher. It has a number of HD = necromancer's class level. Add 1/2 of the necromancer's class level to the skeleton's natural armor bonus. Add 1/3 of the necromancer's class level to the skeleton's Str and Dex. Trade-off: permanently give up ability to have a familiar.
Undead Apotheosis: At 5th lvl, get +2 on saves vs. sleep, stun, paralysis, poison & disease. Bonus becomes +4 at 15th lvl. At 10th lvl, get +4 on saves vs. ability damage, ability drain and energy drain. At 20th lvl, get 25% resistance to crits,as the light fortification armor special ability. Trade-off: Do not gain bonus feats for advancing as a wizard.
Enhanced Undead: Any time the necromancer creates undead, all undead creatures created get a +4 enhancement bonus to Str and Dex and 2 additional hp per hit die. Trade-off: Give up additional spells per day for being a specialist.