Create Vampire

8th-level necromancy
Casting time: 8 hours
Range: 10 feet
Target: A willing humanoid within range
Components: V, S, M (a collection of rubies worth at least 1,000 gp and a liter of blood, both of which the spell consumes, as well as the fang of a vampire, a wooden stake, and a desecrated holy symbol)
Duration: Instantaneous
Classes: Warlock, Wizard
Subclasses:

You can cast this spell only at night. If it becomes daytime while you cast the spell, the spell fails. When you begin casting the spell, a willing humanoid within range dies. When you finish casting the spell, that creature returns to life as a vampire and gains the benefits of a long rest. It retains its personality, alignment, hit points, racial traits, class features, and ability scores, though it changes in the following ways:

• Its creature type becomes undead (shapechanger), and it loses its other creature types.

• It no longer requires air. If its Strength score is lower than 16, it becomes 16.

• Drinking a liter of blood provides it enough nourishment and hydration to sustain it for a full day.

• Its true form is considered to be its vampire form for the purpose of spells and other magic effects.

• It can’t enter a residence without an invitation from one of the occupants.

• It takes 20 acid damage if it ends its turn in running water.

• It takes 20 radiant damage when it starts its turn in sunlight. While in sunlight, it has disadvantage on attack rolls and ability checks.

• If a piercing weapon made of wood is driven into its heart while it is incapacitated, it is paralyzed until the stake is removed.

• It can climb difficult surfaces, including upside down and on ceilings, without needing to make an ability check.

• If it has consumed a liter of blood within the last 24 hours, it has at least 1 hit point, and it isn’t in sunlight or running water, it regains 10 hit points at the start of each of its turns. If it takes radiant damage or damage from holy water, this benefit doesn’t function at the start of its next turn.

• While it isn’t in sunlight or running water, it can use its action to polymorph into a Tiny bat or back into its vampire form. While in bat form, it can’t speak, its walking speed is 5 feet, and it has a flying speed of 30 feet. Its statistics, other than its size and speed, are unchanged. Anything it is wearing transforms with it, but nothing it is carrying does. It reverts to vampire form if it dies.

• Its bite becomes a natural weapon, which it can use to make unarmed strikes. If it hits with its bite, it deals piercing damage equal to 1d6 + its Strength modifier and 3d6 necrotic damage, instead of the bludgeoning damage normal for an unarmed strike. The target’s hit point maximum is reduced by an amount equal to the necrotic damage dealt, and the vampire regains hit points equal to that amount. The reduction lasts until the target finishes a long rest, and dies if its hit point maximum is reduced to 0. The vampire can use this bite attack no more than once each turn.

You can cast this spell targeting a willing vampire created with it to revert all of the changes caused by the spell and return it to its humanoid form.