Starting at 2nd level when you take this subclass, you can add 1 necromancy spell to your spellbook for free. Whenever you gain a level in this class, you may add another necromancy spell to your spellbook for free.
Additionally, the time and gold it takes you to copy necromancy spells into your spellbook is halved.
At 2nd level, when you affect a creature with a spell, you can put a mark on them. You can only have one creature marked at a time, if you mark a new creature while you already have a creature marked, the old creature is no longer marked. The mark lasts for 1 minute or until the creature dies. If the creature dies while marked by you, you regain hit points equal to your proficiency bonus + your intelligence modifier.
At 6th level, you add the Animate Dead spell to your spellbook if it is not there already. When you cast Animate Dead, you can target one additional corpse or pile of bones, creating another zombie or skeleton, as appropriate.
Whenever you create an undead using a necromancy spell, it has additional benefits:
The creature's hit point maximum is increased by an amount equal to your wizard level.
The creature adds your proficiency bonus to its weapon damage rolls.
Beginning at 10th level, you have spent so much time dealing with undead and the forces that animate them that you have become inured to some of their worst effects. You have resistance to necrotic damage, and your hit point maximum can't be reduced. Additionally, when you are dropped to 0 hit points, you may choose to drop to 1 hit point instead and have one of your animated dead die in your place.
Starting at 14th level, you have an aura of death around you. All undead creatures have disadvantage on melee attack rolls against you, and any enemy creature that enters a space within 5 feet of you or ends it's turn within 5 feet of you takes necrotic damage equal to half your Wizard level.