How many spiders can a player character have through class features, spells, etc?

Question

I've been considering making a character who is obsessed with spiders! I want to know how many spiders a player character can have at any one time through spells, class features, etc. (so not by collecting or befriending or taming existing spiders, since that could be infinite spiders given enough time).

Assume that the character is level 20, and that they have whatever ability scores are necessary for multiclassing, etc.

I will place the following allowances and restrictions on this build:

• Becoming a spider, whether via Wild Shape or polymorph, counts as one spider;
• For the purposes of something like find steed, since it says "(Your GM might allow other animals to be summoned as steeds.)", we can assume that the DM is up for this and that a Giant Spider is on the table as a possible mount;
• Hence the spiders don't need to be "Beast" type creatures, summoned spirits in the shape of spiders count;
• That said, as above, the spiders must come from class features, spells, magic items, etc, so no gathering existing spiders, even via charm beast, dominate monsters, etc.
• No help from friends (unless they are being polymorphed into spiders by you);
• Feats and Epic Boons are allowed, but no Unearthed Arcana for this one (largely because of the Swarmkeeper ranger, because swarms get complicated; I'm less strict about other UA though...)
• Magic items are allowed, but I'm excluding spell scrolls, since otherwise we can essentially have infinite castings of mass polymorph or whatever;
• Since it came up in comments, for the purposes of pixies summoned via conjure woodland beings casting polymorph, according to this Q&A, they can keep concentration after being dismissed, but probably won't, so I'm ruling that pixies will stop concentrating after being dismissed;
• No "rinse and repeat" solution for infinite spiders like casting true polymorph each day;
• Hence this must be something that should be achievable within one day (so you start the day with 0 spiders; how many do you have by the end of the day?);

Answer 1

Distant Animal Shapes: ~57 905

Our character is a Druid 15/Sorcerer 3 for animal shapes and the Distant Spell Metamagic respectively.

Animal shapes lets us transform any number of willing creatures within range into spiders:

Choose any number of willing creatures that you can see within range. You transform each target into the form of a Large or smaller beast with a challenge rating of 4 or lower.

We can use Distant spell to double the range of the spell, so the theoretical limit to number of creatures becomes the number of creatures we can pack into a 60 ft. sphere around ourselves. Assuming each Tiny creature occupies a 2.5 ft. cube, that becomes approximately (ignores space needed for the caster): $$ \frac{4}{3}\times\pi\times60^3\times\frac{1}{2.5^3} \approx 57,905 $$ Coercing those non-spider creatures is left as an exercise to the caster.

Animal shapes requires concentration, however we can add two more spiders via find familiar and Wild Shape.

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Burrowing David Coffron's simulacra method, an 18th level Bard (+2 levels of something) and Boon of High Magic, and simulacrum, animal shapes, and wish can create 14 400 simulacra who all have a 8th level slot for animal shapes. As these don't have Distant spell, each spell can only do ~7 238 tiny creatures into spiders, but for a grand total of 104 227 200. (space for caster/simulacra or use of find familiar etc. not accounted for).

Answer 2

A total of 36 Spiders

As an attempt at answering this myself, here's what I've come up with:

• Druid 5 for Wild Shape and conjure animals;
• Ranger 3 for a companion via Beast Master;
• Lore Bard 6 for find familiar and find steed;
• Remaining levels in any full caster class for a 9th level spell slot;

So that's

• 32 spiders summoned via conjure animals (if cast with our 9th level spell slot)
• 1 Giant Spider mount from find steed;
• 1 spider familiar from find familiar;
• 1 Giant Wolf Spider animal companion from Beast Master ranger;
• 1 from using Wild Shape to turn yourself into a spider.

For a total of 36 spiders, including yourself (for as long as your concentration on conjure animals lasts, and as long as Wild Shape lasts).

Answer 3

Virtually no limit

If you are a level 17 wizard, with the simulacrum, wish, and polymorph spell can have any number of spiders.

By using wish to create simulacra, as detailed in this answer to a different Q&A, you can have essentially unlimited versions of yourself. Have each simulacrum cast polymorph to become a spider of choice, and you are all set.

To illustrate the procedure more clearly, here you are:

1. Cast simulacrum normally. (you, and therefore the simulacrum, will still have a 9th level spell slot)
2. Have the new simulacrum cast wish to replicate the effect of simulacrum targeting you. (this will create another simulacrum that is missing a 7th level slot but still has a 9th)
3. Have the simulacrum that cast wish order the new simulacrum to cast polymorph at a specified time.
4. Repeat until you have the desired number of simulacra each with their orders.
5. Wait until the specified time, and watch as your army of spiders is formed.

If you are limited to one day for creating simulacra (rather than just requiring that you have no spiders at the start of the day), you are better off with the Boon of High Magic and casting wish to create the first simulacrum (since casting it normally takes half the day on its own). This gives 14,400 simulacra in one day.

Maximum spiders in one day

If you also get 2 levels of druid for Wild Shape, these spells...

• find familiar
• conjure animals (via the Gruul Anarch background from Guildmaster's Guide to Ravnica)

...and the Epic Boon of High Magic, you can increase the one-day count even more, by having each simulacrum cast these spells (conjure animals at 8th level) before transforming with Wild Shape.

With this, each simulacrum yields:

• 1 spider from find familiar
• 1 spider from transforming with Wild Shape
• 24 spiders from conjure animals at 8th level.

...and you give:

• 1 spider from find familiar
• 1 spider from transforming with Wild Shape
• 36 spiders from conjure animals at 9th level (using the Boon of High Magic slot).

This would give a grand total of 374,438, but the simulacra create in the last hour don't have time to cast find familiar reducing the count to 374,078.

Conjure Animals Spell Glyphs might be usable

The count could be increased quite a bit more, if glyph of warding can create Spell Glyphs of conjure animals. The text of conjure animals says (*emphasis mine):

You summon fey spirits that take the form of beasts and appear in unoccupied spaces that you can see within range.

...and the requirement for a Spell Glyph is:

The spell must target a single creature or an area.

Since animal shapes reads that it targets multiple spaces, it is likely not a valid spell for Spell Glyph. However, if you are summoning only one creature with animal shapes, one could interpret that you are only targeting one unoccupied space, which would be valid for Spell Glyph.

If this interpretation is used, you should sacrifice Wild Shape to get to level 20 wizard for Signature Spells (choosing glyph of warding). While we don't get to transform the simulacra without Wild Shape, the additional Spell Glyphs more than make up for it.

Each simulacra and you now give:

• 24 spiders from conjure animals.
• 1 spider from find familiar for each simulacrum that has at least 1 hour.
• 1 spider for each additional hour beyond the first, up to 7 spiders from Spell Glyphs of conjure animals (this exhausts the spell slots of level 3 and higher the simulacrum has, as well as the first usage of Signature Spells with the final spell slot)
• 1 spider for each additional 4 hours beyond 7; the simulacrum saves the spell slots that would be used on glyph of warding to instead rest and use Signature Spells twice.

This results in the following table for the number of hours each simulacrum has to make spiders, and how many spiders they make:

\begin{array}{c|c|c} \hline \text{Number of Hours} & \text{Number of Simulacra} & \text{Number of Spiders} \\ \hline 0 & 600 & \text{14,400}\\ \hline 1 & 600 &\text{15,000}\\ \hline 2 & 600 &\text{15,600}\\ \hline 3 & 600 &\text{16,200}\\ \hline 4 & 600 &\text{16,800}\\ \hline 5 & 600 &\text{17,400}\\ \hline 6 & 600 &\text{18,000}\\ \hline 7 & 600 &\text{18,600}\\ \hline \text{8-10} & \text{1,800} &\text{57,600}\\ \hline \text{11-14} & \text{2,400} &\text{79,200}\\ \hline \text{15-18} & \text{2,400} &\text{81,600}\\ \hline \text{19-22} & \text{2,400} &\text{84,000}\\ \hline 23 & 600 &\text{21,600}\\ \hline \end{array}

...this gives a grand total of 456,000.