I remember a 5e aoe spell that would "eat" corpses in the area of effect.
I thought it was Hunger of Hadar, but after looking it up I found I misremembered that.
So, my question is if you a evil spell caster trying to cover up your tracks what spell is good for disposing of bodies?
The lower the level the better.
One of the most useful cantrips is Mold Earth:
You choose a portion of dirt or stone that you can see within range and that fits within a 5-foot cube. You manipulate it in one of the following ways:
And the interesting way for this purpose is:
If you target an area of loose earth, you can instantaneously excavate it, move it along the ground, and deposit it up to 5 feet away. This movement doesn’t have enough force to cause damage.
If you have a very strict DM, you might be required to dig a hole first, then dump the body in there, then cover it up again. If you have less strict DM, they probably allow you to excavate the ground from under the corpse, then when the hole is deep enough, fill it up on top of the corpse.
Note that the earth needs to be loose enough, so you may need quite a few castings to dig a hole deeper than 5 feet. But if 5 feet is enough, it takes just 12 seconds to bury the corpse.
To finalize effect, especially if you are in a hurry and don't want to dig deeper than 5 feet, or if you want to cover up the signs of digging, you may consider a 3rd level spell, Plant Growth:
If you cast this spell using 1 action, choose a point within range. All normal plants in a 100-foot radius centered on that point become thick and overgrown. A creature moving through the area must spend 4 feet of movement for every 1 foot it moves.
You can exclude one or more areas of any size within the spell's area from being affected.
Unless whoever is looking for the corpse is very determined and knows what they are looking for, the chances are the corpse will not be found before it decomposes.
Of course these don't actually Disintegrate the corpse or deposit it in a Demiplane or something else which immediately erases all traces, but Mold Earth is just a cantrip (Plant Growth is bit harder to come by, but not super rare). Advantage over fire spells like Create Bonfire is, that burying is probably much faster (maybe just 2 rounds), than completely ashing the corpse, and isn't quite as obvious as a bonfire smelling of burning flesh and giving a thick column of smoke.
Animate dead is a 3rd level spell and you're already an evil caster so you're not going to spend time wondering if you should be creating more undead.
This spell creates an undead servant. Choose a pile of bones or a corpse of a Medium or Small humanoid within range. Your spell imbues the target with a foul mimicry of life, raising it as an undead creature.
Since your question is how to dispose of a corpse, once you've got it up and walking you can have it (as examples):
After all...
You decide what action the creature will take and where it will move during its next turn, or you can issue a general command, such as to guard a particular chamber or corridor.
Of course, as a caveat:
The creature is under your control for 24 hours, after which it stops obeying any command you’ve given it.
...so you'll want to make sure it's actually disposed of before those 24 hours are up.
It makes sense to get rid of the corpses of your enemies, especially if the innocent townsfolk you live amongst don't know you're evil, a caster, or both. But maybe you eventually decide you deserve an evil tower, or an evil dungeon. Now those corpses, instead of a burden you need to dispose of, are free labor! So if you're learning one spell for corpse disposal now, make it Animate dead and invest in your future.
Among the official published content of DND 5e, I was not able to find any spells to dispose of corpses, and in my search of UA material I found nothing as well. However, there are many spells that may be used to dispose of a corpse magically, depending on the leniency of your dungeon master.
Human skin receives first degree burns at 118 Celsius (244 Fahrenheit), and is destroyed at 162 Celsius (323 Fahrenheit); I assume flesh and the other parts of humans excluding bone burn at a similar temperature, though I don't want to add too many of these searches to my google algorithm. A crematorium typically operates between 760-980 Celsius (1400-1800 Fahrenheit), and burns for between 3 and 4 hours. It is up to your DM what temperature a fire spell is cast at, and whether it is hot enough to completely destroy a corpse, or how long you will need to be casting the spell for. Let's use the Commoner's stat block for a baseline: 4hp will be what we assume the average human has for health, and will be instantly killed if they receive 8hp of damage. Our best cantrip to burn bodies is likely Create Bonfire:
Create Bonfire
You create a bonfire on ground that you can see within range. Until the spell ends, the magic bonfire fills a 5-foot cube. Any creature in the bonfire's space when you cast the spell must succeed on a Dexterity saving throw or take 1d8 fire damage. A creature must also make the saving throw when it moves into the bonfire's space for the first time on a turn or ends its turn there.
The bonfire ignites flammable objects in its area that aren't being worn or carried.The spell's damage increases by 1d8 when you reach 5th level (2d8), 11th level (3d8), and 17th level (4d8).
The starting damage, 1d8, averages to 4.5hp. This would be enough average damage to outright kill an unconscious commoner. As your level increases, so too does the spells damage, however there is no clarification as too why the damage increases; it could be the spells temperature increasing, or it could be the size of the fire increasing (while remaining inside its 5-foot cube). This is up to your DM, but it is a good candidate for cremating bodies at higher levels, though it may need to be recast for up to 4 hours to complete the process.
A few leveled spell you may consider:
A bit higher level of a solution, but potentially a perfect solution, if your evil spellcaster is able to get a hold of a gelatinous cube.
Teleportation Circle (5th level): Another spell that only effects creatures, but there is no reason for this spell not to effect objects; Raise the corpse as an undead, then have them enter the circle. Cast a teleportation circle onto a heavily slanted platform set above a 10-foot square pit for a year, until the circle is permanent. put a gelatinous cube in the pit. Anything that is teleported to the circle is immediately dumped into the gelatinous cube, and dissolved.
Teleport (7th level): Same as above, except this spell is already approved to teleport objects, and you don't need a year to set up the circle, as long as you have an associated object from the pit's location. While you can only teleport one object at a time, "a trunk with 5 bodies in it" counts as one object.
This will assume you are able to bring all of your victims, pre- or post-death, to the same location, and you have more than 1 victim. Animate Dead, Danse Macabre, Create Undead, and Finger of Death all create a undead creature of some sort, under your command. Command the resulting undead to "destroy all other corpses or undead, then pulp there bodies, then destroy yourself." Maybe put them in a room with a meat grinder, and teach the undead how to grind the other bodies? I'm sure there is a bit more magical option then that.
Disintegrate (6th level):
A creature targeted by this spell must make a Dexterity saving throw. On a failed save, the target takes 10d6 + 40 force damage. The target is disintegrated if this damage leaves it with 0 hit points.
A disintegrated creature and everything it is wearing and carrying, except magic items, are reduced to a pile of fine gray dust. The creature can be restored to life only by means of a true resurrection or a wish spell.
This spell automatically disintegrates a Large or smaller nonmagical object or a creation of magical force. If the target is a Huge or larger object or creation of force, this spell disintegrates a 10-foot-cube portion of it. A magic item is unaffected by this spell.
This is a great option for a single corpse or creature, as it will be able to cleanly destroy the evidence in one shot. All that's left is a quick gust of wind spell to blow away the pile of ash that remains.
