How can I have low-level 5e necromancer NPCs controlling many, many undead in this converted adventure?

Question

I require as close to a RAW answer as possible for ~Level 5 Wizard(s) to control ~100 skeletons and zombies.

Context: I'm adapting a few classics for older editions to D&D 5e, and running into issues for which I need RAW solutions. I could just hand wave it away but my own DM does that sort of thing and I am very much a proponent of what I call the Goose and Gander argument for players and NPCs: essentially, (with a few exceptions) if the bad guy can do it then so can the players, given enough time and resources. So handwaving the NPCs' abilities doesn't work for my campaign.

The AD&D 2e adventure Return to the Keep on the Borderlands has a Necromancer and several large groups of skeletons and zombies, but there is no possible way that the denizens of the temple could maintain control of so many for what they are utilized.

All told there seems to be ~100 skeletons and zombies that are described as being controlled, i.e. they have tasks they are performing when encountered. The module only describes a single caster that would be capable of casting Animate Dead and it is a 5th Level Wizard (Necromancer) there are a handful of lvl 3 Clerics in there as well. This technically would not have worked even in 2nd edition RAW since Animate Dead was 5th level for Wizards. I would however like to have at least a modicum of a better explanation than "Well, that's what was written in the module."

Therefore, is there something out of all the books that I am missing that could justify a small, essentially low level temple having so many controlled undead?

Immediate thoughts would be replacing some of them with constructs. Given the nature of the temple Scarecrows are the obvious choice and would be controlled indefinitely. I did see some ideas about converting the Bone Golem from previous editions — the problem with that is it changes the focus from Necromancy to Conjuration (as Scarecrows are bound spirits), which is not really desirable nor as interesting a threat to the good NPC side.

I also thought of scrolls but they are limited and would need to be replenished somehow from a higher level wizard that can make them. This option would require many scrolls, possibly dozens, per day if the existing casters capable of scribing them were to be the ones creating them.

I don't see a way of doing this without a custom magic item, something akin to the 3.0 whistle from Sunless Citadel.

Answer 1

I see two broad options, one of which is a bit of a frame-change.

First, the frame change: most undead - especially low-level undead like zombies and skeletons - were mindless in previous editions of D&D and aren't terribly bright in 5E. It shouldn't be too hard for some passably persuasive denizens to convince the undead hordes to follow their commands without magic. Further, zombies and skeletons are frequently portrayed as basically milling about doing nothing in particular if there's nothing better to do; it shouldn't be too hard for the denizens to have corralled the undead into holding areas for later use (it's not like they need food or exercise, after all).

Option 1b, I guess, would be that there's no particular reason for the undead creatures to stop doing whatever it was that they were doing when they're no longer controlled, especially if what they were doing is a mindless, repetitive task ("keep turning this wheel" or "walk along this round pathway (ie., patrol)").

If that's not quite sufficient, the denizens could be keeping a handful of key undead creatures under their control, and trusting that the rest of them will just kinda follow along.

PCs could, in principle, do the same thing: control or convince (or just lure) the undead to where you need them to be, then let them hang out there 'til they're needed. If necessary, keep a small number under control for specific purposes.

The second option would be to adjust (slightly) the Hallow spell, and "Un-Hallow" the area (which may indicate that a more powerful creature is behind this, and the adventure is prelude). As written, Hallow appears designed for Good PCs to use; I don't see why its mirror shouldn't exist, which would allow for necromancers to exert some control over more undead than normal (possibly only just "some" control, though: perhaps it's just enough that the undead see the other denizens as "friendly" as opposed to "lunch").

Again, in principle a PC could do this, if they could find a deity willing to allow it.

Answer 2

Frame challenge ahead (you have been warned)!

if the bad guy can do it then so can the players, given enough time and resources.

This is a very un-5e thing to say - it looks very 3e to me.

5e makes it clear that monsters/NPCs are not like PCs and that they can do things that the PCs cannot do and vice versa. The NPCs in the Monster Manual are impossible to create using the rules for PCs.

Embrace this and create the following NPC feature:

Necromantic Nexus You straddle the divide between life and death. As such your ability to control undead is enhanced you can [whatever the heck you need to make the plot work].

This is completely in line with RAW: NPCs are meant to be challenges for the PCs, not their surrogates.

Answer 3

Make a high level wizard that behaves as a low level wizard

There is one characteristic about wizard that are common through every D&D game, they are extremely squishy, especially if they are badly built or they used all their spells before a fight. A wizard without spells is not different than a level 1 fighter with more hp, maybe better to hit chance and, probably, worse AC. Another thing, by RAW the spell Animate Dead and Create undead apply a spell slot tax to maintain the the undead horde, this will reduce the number of spells that the wizard may cast.

Animate Dead: To maintain control of the creature for another 24 hours, you must cast this spell on the creature again before the current 24-hour period ends.

There are some consideration to have so the "high level" wizard maintain a reasonable challenge rating. There are 3 particular things to look for; cantrips, intelligence and spell slots, and proficiency bonus.

Cantrips

In this edition all attack cantrips rise in power as the wizard increase in levels, but it is done at specific levels: at 5, 11 and 17. The minimum level of the wizard is 5, since Animate Dead is a level 3 spell, therefore one possible level to keep it as low as possible is 10 or at most 16.

Firebolt: This spell's damage increases by 1D10 when you reach 5th level (2D10), 11th level (3D10), and 17th level (4D10)

Intelligence and spell slots

In 5e intelligence does not increase the number of spell slots that a wizard may have and the cap for each spell level is achieve quite fast. For example, at level 4 the maximum spell slot for level 1 and 2 spells are reached, and at level 6 level 3 spells are maxed out (Table on PHB 113). This implies that increasing intelligence will not impact the spell progression, only the chance to hit with spells, DC and INT related saves and skills. A well built Wizard would have INT capped at level 8.

Proficiency bonus

To make it short, the relevant capstone for proficiency bonus are 9 and 13 since 5 is absolutely necessary for Animate Dead by RAW.

Wizard apparent level

Aside for HP and the capstone discussed previously, what really limits the apparent level of the wizard is the spell at his disposal. An example on a level 6 wizard, If we use every single third level spell slot we can have 12 zombies, four for each third level spell slot, the apparent level would be 4. Yes, bounded accuracy is a thing in this edition, but depending on the spells this might not even matter (e.g. Magic Missile: no save, no DC and not miss chance)

Animate Dead: At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, you animate or reassert control over two additional undead creatures for each slot level above 3rd.

Magic Missile: You create three glowing darts of magical force. Each dart hits a creature of your choice that you can see within range.

Number of undead by capstone

Since the objective is to have the maximum number of undeads while keeping a low apparent level as possible, all high level spell slots are used to cast animate dead:

• At Level 7 (pre ASI): 12 + 6 = 18 (3 level 3, 1 level 4)
• At Level 8 (pre proficiency bonus): 12 + 12 = 24 (3 level 3, 2 level 4)
• At level 10 (pre cantrip damage increase): 12 + 18 + 16 = 46 (3 level 3, 3 level 4, 2 level 5)
• At level 12 (pre proficiency bonus): 12 + 18 + 16 + 10 = 56 (3 level 3, 3 level 4, 2 level 5, 1 level 6)

At level 10, the wizard is capable of keeping 46 undead under his command by RAW, while maintaining the same spells as a level 4 wizard. An example of a hampered wizard would be:

Half elf level 10 Wizard (Average HP: 32 (6 + 36 - 10 [-1 con])

• STR: 9
• DEX: 12 (11+1)
• CON: 8
• INT: 20 (15 + 1 + 4)
• WIS: 14
• CHA: 16 (14 + 2)

This would yield a +2 DC and hit over a level 5 wizard with the same INT progression, and the same 32 HP that a level 3 Fighter with CON 14 would have. Nothing impressive if you ask me (aside for the sheer number of undeads).

Tips

• Multiclass: If you multiclass with, for example, a Death Domain Cleric, it won't hamper the spell slot progression but it will diminish some benefits of the level 6 and a 10 wizard schools capstone. This even apply a little MAD and would be thematically relevant. It would gain more HP and a better AC with armor, this might be good since it would not be so squishy.
• More squishy wizards more undeads: 4 wizards can control almost 200 undeads and they don't need to fight the party at the same time.
• Keep calm, build them bad: The more you mess with the built, the weaker and more challenge appropriate it will be. "Bad" choices would make some good RP elements (mistakes happen to everyone, maybe a level in sorcerer was not his best idea).

Answer 4

The simplest solution I have found whenever I need an NPC to be able to act outside of the normal rules governing their class and level is by the expediency of a customized magic item.

As a matter of fact, I have recently used exactly this sort of magic item to solve exactly this sort of problem. I needed a medium level NPC to have the potential of leading hordes of undead, or at least numbers of undead greater than their level would allow. This was done with the introduction of an item with severe necromantic enhancing powers. I made sure that there were enough drawbacks to it that would make it unappealing to the PCs once it fell into their hands upon the defeat of the villain, without inconveniencing the NPC villain (specifically, it recharged through acts of murder).

But the upshot of this is that I was able to keep the rest of the NPC's build entirely book legal, keeping him at a low enough level to allow him to be beaten by the PCs while commanding the powers that the plot required.

The emphasis on RAW was increased since I answered this question. However, since the creation of magic items is RAW within the DM's purview, and since the answer contains the way to keep this power out of the PC's hands, (which was a stated concern), I decided to let it stand.

Answer 5

Why not have the temple/building/whatever itself be the source of the undead? Hundreds of years ago, the monks of the Temple of Poking Fun at the Death God did something to make the Death God angry, so he cursed them to never know the afterlife. They were struck down one night, only to rise as various undead, and go about their normal tasks for eternity. As the party kills them, you could have the spirits thank them or something to add in this effect.

This prevents the players from ever being able to control those masses of undead (because a God did it) and if you need a reason for the necromancer to control any, he could have created those undead specifically himself (or impersonate some higher up monk or something).