Alter Undead

Your mastery of creating undead has allowed you to make changes to the physiology.

Your DM may decide that you can cast this spell during a long rest (for convenience of play). Choose one willing undead within range; they gain one of the following benefits.

• Extra Arm: This creature can make an extra attack as part of the Attack action, and creatures have disadvantage on checks made to escape a grapple made by this creature.
• Body Armor: The creature gains natural armor. Their AC increases by an amount equal to your Intelligence modifier. 
• Arcane Runes: The creature gains the ability to cast a cantrip that you know. Use its Intelligence modifier to calculate spell save DC and bonus. The creature does not need to provide verbal or somatic components if it doesn't have hands or can't speak. 
• Natural Weapons: The creature's unarmed attacks now deal 1d4 bludgeoning, piercing, or slashing damage. If the creature already dealt a die of damage with its unarmed attack, move up to the next biggest size of die. (Ex. d6 becomes a d8).
• Death Burst: When this creature dies, it explodes in a 10-foot radius. Every creature in this radius must succeed on a Dexterity saving throw or take 4d6 fire, lightning, acid, cold, or thunder damage (decided when you cast this spell)
• Speed: The creature's speed increases by 5 feet.

Once you cast this spell on a creature, you cannot alter it again unless you first cast this spell to undo the first alteration. If you cast this spell at 8th level, you may either add another alteration listed above or add an alteration listed below. A creature can only have a maximum of two alterations. You must use golden thread worth at least 200 gp if you cast this spell at 8th level.

• Flight: You may only add this alteration to creatures with the Speed alteration. The creature gains a flying speed of 30 feet and can hover. 
• Size: You may only add this alteration to creatures with the Natural Weapons alteration. The creature increases its size by one category. Its maximum hit points increase by 2d10, its Strength score increases by 2, and it deals an extra die of damage with all attacks.
• Advanced Runes: You may only add this alteration to creatures with the Arcane Runes alteration. The creature gains the ability to cast one 1st-level spell that you know. The creature can cast this spell once per long rest. 

This spell can only be found within the pages of the Book of Vile Darkness. Any attempt made to transcribe this spell onto another medium is met with failure; unexplainable circumstances prevent the spell from being copied. Only creatures in possession of the Book of Vile Darkness can cast this spell.