Several spells from the infamous Book of Vile Darkness converted into 5e.
You could use them in the following ways:
-Add them to the original spellcasting list of an Evil PC, most likely in an evil campaign
-Add them to the spellcasting list of an Evil NPC
-Allow PCs to stumble over a vile scroll containing these spells
-Simply include these spells in the in-game Artifact 'Book of Vile Darkness' so that the PCs can use them
So, here we go:
Darkbolt
2nd-level Evocation
Components: V, S
Casting Time: 1 action
Range: 90ft
Target: One creature
Duration: Instantaneous
The caster makes a ranged spell attack against a foe, launching a bolt of cold darkness from his left hand. The bolt deals 4d8 damage with no specific type. When struck, the foe must also succeed at a Constitution Saving Throw or be stunned for his/her next turn, overwhelmed by the evil charge of the darkbolt.
At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the damage increases by 1d8 for each slot level above 2nd.
Unliving Weapon
3rd-level Necromancy
Components: V, S, M (pinch of sulfur)
Casting Time: 1 action
Range: 30 feet
Target: One undead creature
Duration: 1 hour (concentration)
This spell causes an undead creature to explode in a burst of powerful energy when struck for at least 1 point of damage, or at a set time no longer than the duration of the spell, whichever comes first. The explosion is a 15-foot-radius burst that deals 8d6 necrotic damage.
While this spell can be an effective form of attack against an undead creature, necromancers often use unliving weapon to create undead capable of suicide attacks (if such a term can be applied to something that is already dead). Skeletons or zombies with this spell cast upon them can be very dangerous to foes that would normally disregard them.
At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, you can target 1 additional undead creature for each 2 slot levels above 3rd.
Curse of the Putrid Husk
3rd-level Illusion
Components: V, S, M (powdered human bone)
Casting Time: 1 action
Range: 30 feet
Target: One creature
Duration: 1 hour (concentration)
This illusion forces the subject to believe his flesh is rotting and falling off his body, and that his internal organs are spilling out. If the target fails his Wisdom saving throw, he is horrified during his next round, suffers from the Stunned condition, and takes 1d8 necrotic and 1d8 psychic damage. During each of the end of the target’s turns, the target can repeat his Wisdom saving throw (the difficulty of the saving throw decreases by 1 every round). Also, when the target takes damage, he can repeat his Wisdom saving throw with disadvantage (this is because the damage may contradict with the illusion - for instance, the damage inflicted may cause pain in an arm that the target believes has already rotted off). If the target succeeds on any of these saves, the spell ends. If he fails, he again takes the damage listed above, and remains horrified (stunned).
Wall of Flesh
6th-level Conjuration
Components: V, S, M (body parts of a zombie)
Casting Time: 1 action
Range: 100 feet
Duration: Instantaneous
A disgusting wall made of rotting flesh springs into existence at a point you choose within range.
The wall is 6 inches thick and is composed of ten 10-foot-by-10-foot panels. Each panel must be contiguous with at least one other panel. If the wall cuts through a creature's space when it appears, the creature is pushed to one side of the wall (your choice). If a creature would be surrounded on all sides by the wall (or the wall and another solid surface), that creature can make a Dexterity saving throw. On a success, it can use its reaction to move up to its speed so that it is no longer enclosed by the wall. This wall can be used to seal off a passage or close a breach, for the wall inserts itself into any surrounding nonliving material if its area is sufficient to do so.
Eyeballs, ears, noses and mouths spring to the surface of the wall. Arms and legs may sprout as well. The five senses of the wall – except for touch (and pain) – are immediately transmitted to the caster.
Each 10-foot section of the wall has 25 HP per inch of thickness and AC 12 (normally 150 HP). A section of wall brought to 0 hit points is breached.
Any creature which makes physical interaction with the wall (including melee weapons and touch magic) takes 1d6 points of necrotic damage from the corrosive nature of the rotting flesh and the haunting moans. Only the surrounding material that the wall initially is conjured to touch—such as the floor or an adjoining wall—is immune to this damage.
Furthermore, organic material (such as creatures) that directly touch the wall must succeed at a Constitution saving throw or be paralyzed. The wall then consumes the creature in 3 rounds, digesting it and adding the creature’s full normal hit point total to its own. The player can repeat the Constitution saving throw during each of his turns to escape this.
Death by Thorns
7th-level Conjuration
Components: V, S
Casting Time: 1 action
Range: 25 feet
Target: One creature
Duration: Instantaneous
The caster causes thorns to sprout from the insides of the subject creature, which writhes in agony for 3 rounds, incapacitated and taking 6d6 points of piercing damage at the start of each of his turns, before his HP immediately hit 0, with 1 already failed Death Saving Throw. During the 3 rounds of effect, the target makes a Constitution saving throw during each of the end of his turns, ending the above effects on a success.
However, a creature that succeeds at his Constitution saving throw is still cursed by the thorns for 1d6 extra turns. During this time, he takes 3d6 points of piercing damage at the start of each of his turns. Also, even the slightest movement inflicts terrible pain to the target – resulting in 1d4 damage for each attack or spell attempted, and 1d4 damage for each 5 feet the target moves. In addition, the moving speed of the target is halved during this time.
A Wish spell cast on a subject during this time can eliminate the thorns and completely save the creature. In this case, the thorns do not linger, ending all effects of this spell.
Apocalypse Spell
9th-level Necromancy
Components: V, S, M (the severed head of a Good humanoid)
Casting Time: 1 action
Range: 30-mile radius, centered on caster
Duration: Instantaneous
The caster calls upon the darkest forces in all existence to rain destruction down upon the land. All creatures and objects in the spell’s area take 10d6 points of fire, acid, or poison damage (caster’s choice), and 10d6 points of necrotic damage. This damage typically levels forests, sends mountains tumbling, and wipes out entire populations of living creatures. The caster takes half of this damage.
In addition, crimson clouds quickly gather overhead, and unleash a horrible rainstorm of blood that covers the area. The blood pours down in thick drops, coating everything in a dark red, sticky mess. Any living, non-evil creature in the area of a rain of blood must succeed at a Constitution save or take a –1 penalty on attack and damage rolls, checks, and saves for 24 hours. Undead, and any evil creatures the caster controls gain a +1 bonus on attack and damage rolls, checks, and saves for 24 hours if they are in the area of the rain, or if they are summoned in the area of the rain.
Comments and constructive critisism greatly appreciated.