Libram of Flesh and Souls

Wondrous item - requires attunement by a wizard
Made of magically reinforced parchment and bone, written in neatly inked Giant and bound in leather of dubious origin.
While attuned to the spellbook, the scribed spells in bold below are intrinsically understood by you, and may be prepared as though the Libram is your spellbook even if you did not scribe them.
The book has 3 charges, and regains 1d3 expended charges at dawn. While holding the spellbook, you may expend a charge for either of these abilities:

If you spend 1 minute studying the book, you can replace one prepared Wizard spell with a spell in the Libram that is from the Necromancy school.

As an action, you take on a semblence of undeath. For 10 minutes, or until you deal damage or force a creature to make a saving throw, you appear undead to outward inspection and magic used to determine your status. Undead creatures normally hostile to life are instead indifferent to you, unless you have damaged them.

The book contains the following spells scribed into it:
1st Level: false life, ray of sickness, expeditious retreat, mage armour, shield
2nd Level: acid arrow, mirror image, blindness/deafness, ray of enfeeblement
3rd Level: summon undead, vampiric touch, speak with dead, animate dead, slow, fireball
4th Level: dimension door, vitriolic sphere, blight
5th Level: danse macabre, cloudkill
6th Level: circle of death, create undead
7th Level: finger of death, tether essence