Is there a way to obtain, from one's own spells, creatures that could be True Polymorphed into objects?

Question

TL;DR: How can a character produce, ->via spells<-, creatures that can be True Polymorphed into objects without disappearing later?

[NOTE: for the scope of the question, I am not concerned with the character's class or what spells are available to him. Please consider any spells published in D&D 5e books/supplements as acceptable ingredients for a solution.]

I am interested in a character being able to use True Polymorph to create arbitrarily many objects (max 1 per day, of course) to use as spell components, build his secret lair, etc. The catch is, for black-boxed reasons, he is sequestered away from the world, and can only use resources that have ultimately come from his own spells. So he can only T-P creatures out of creatures or objects that he has previously produced, and only T-P objects out of creatures he has previously produced.

Creating objects to use as fuel looks straightforward. Here's one repeatable example:

1. Cast Demiplane, choosing "stone" as the material of the "empty room". We now have a stone surface.
2. From inside said demiplane, cast Wall of Stone, creating ex nihilo a volume of stone "merging with and solidly supported by existing stone". By concentrating the full ten minutes, the stone wall can no longer be dispelled: it has become permanent, mundane stone.
3. Cast Fabricate to shape objects of desired dimensions out of this stone.

Creating creatures, however, seems to be more complicated than I originally thought, since it seems that, by RAW, one cannot "stack" a second T-P onto a target which already has a (permanent) T-P effect on it. In other words, if I understand this correctly, creatures "created" via object-to-creature T-P are not actually valid targets for a subsequent creature-to-object T-P.

If T-P itself won't give me creatures to use as fuel, where can my character turn?

Conjuration? I've looked into spells that conjure or otherwise summon creatures, but nearly all of them have a limited duration, and (as linked in the "TL;DR") any objects T-Pd from them are liable to disappear after the summoning spell's duration has elapsed. The few that do not expire seem unsuitable for other reasons (Find Familiar/Steed seem to be manifest spirits, and are not called "creatures"; Planar Ally is not a creature of your creation, and would probably not take kindly to an attempted T-P).

Breeding? Suppose we T-Pd a bunch of stones into rats (PHB p.309) and bred them. There are plenty of spells that could provide food and water for them. We would not be able to use any of the initial, generation-0 rats for creature-to-object T-P, but what about the progeny? It seems reasonable to suppose that they could be, and it seems feasible for a character to maintain a cageful of rats, but there's a lot here going well beyond RAW and into the realm of DM fiat.

Is there any better, more explicitly RAW way to obtain creatures for this purpose, using only a character's own spells?

Answer 1

Simulacra are perfect for this

One way to create creatures is to simply create a vast number of simulacra. Any suitable high level wizard can pull it off. Here is the procedure:

1. Cast simulacrum targeting yourself creating sim-one.
2. Take a long rest.
3. Have sim-one cast wish replicating the effect of simulacrum targeting you creating sim-two.
4. Have sim-one instruct sim-two to follow your commands forever as though they came from them.
5. Cast true polymorph on sim-one in any manner you choose.
6. Henceforth, sim-two is referred to as sim-one.
7. Repeat steps 2-6 as often as you want.

Because you use a long rest after casting true polymorph, the simulacra that are wished into existence all have a fresh 9th level spell slot to use for their own wish. The key factor is that they can target you rather than themselves for the simulacrum spell.

The extra benefit of simulacrum is it creates a 20th level character, which can then be formed into any creature of CR 20 or lower with true polymorph. It is far more flexible than any other option for that reason.

Answer 2

The character must be at least level 17 Transmutation Wizard (for Master Transmuter and True Polymorph) and level 2 Artificer (for infusions).

Main Loop:

1. Use the Replicate Magic Item infusion to create the common magic item "Pot of Awakening".
2. After 30 days, get an Awakened Shrub (small plant creature).
3. True Polymorph it into an object no larger than small size.
4. Profit.

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Bare minimum to be strictly RAW, we need to start with an arcane focus.

Each Artificer infusion can only be applied to one object. However, there is some debate regarding whether one can pick the same infusion multiple times for Infusions Known. We'll pick the "Replicate Magic Item - Pot of Awakening" infusion as many times as possible to grow them in parallel.

Pot of Awakening

Wondrous item, common

If you plant an ordinary shrub in this 10-pound clay pot and let it grow for 30 days, the shrub magically transforms into an awakened shrub at the end of that time. When the shrub awakens, its roots break the pot, destroying it.

The awakened shrub is friendly toward you. Absent commands from you, it does nothing.

Replicate Magic Item technically needs us to supply the base object as it mentions:

In the tables, an item's entry tells you whether the item requires attunement. See the item's description in the Dungeon Master's Guide for more information about it, including the type of object required for its making.

Thus, we need to get an ordinary shrub and a clay pot for each cycle. Taking inspiration from How to polymorph one object into another, specifically a pumpkin into a carriage?, we will use the Major Transformation effect from the 14th level Master Transmuter feature:

Master Transmuter

Starting at 14th level, you can use your action to consume the reserve of transmutation magic stored within your transmuter's stone in a single burst. When you do so, choose one of the following effects. Your transmuter's stone is destroyed and can't be remade until you finish a long rest.

Major Transformation: You can transmute one nonmagical object—no larger than a 5-foot cube—into another nonmagical object of similar size and mass and of equal or lesser value. You must spend 10 minutes handling the object to transform it.

I'm not sure how a mass of material will be treated vs a single object (and whether the Wall of Stone counts as one object or you can split it into chunks), but you could either directly transmute into pots, or get a bunch of clay and use Potter's Tools to craft the pots.

The 3rd level artificer feature "The Right Tool for the Job" will let us create Potter's Tools out of nothing if we have thieves' tools/artisan's tools at the start. If the DM allows using an infused item instead of tools for this feature (like how it works for spellcasting), then you can start with just the arcane focus and infuse it to become an Enhanced Arcane Focus.

Similarly we get shrubs and plant them into the infused Pot of Awakening. Based on Are plants creatures or objects, the ordinary shrub should count as an object while the Awakened Shrub is a creature that is valid for True Polymorph.

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We won't be able to learn Create Food and Water as it is a 3rd level Artificer spell, but 45 pounds of food seems like a good target for Major Transformation. I think water is generally not considered an object, so the lower level Create or Destroy Water might not be suitable.

I didn't consider the Awaken spell because it requires 1000gp consumable material, but it opens up the option of a Awakened Tree (Huge plant) which opens up more True Polymorph options maybe.

Enlarge/Reduce works on creatures and objects, but as a temporary effect I doubt it would be affect True Polymorph or result in free increase of a given resource.

Answer 3

Found Creatures

While the spirit you summon with find steed or find familiar may not be a creature, they "take the form of an animal" that is a creature.

This is confirmed by Sage Advice (v. 1.14 p. 14 - emphasis mine):

Does the familiar of find familiar count as an ally for the purposes of Sneak Attack? A familiar is an allied creature. Its proximity to a target can allow you to use the Sneak Attack feature or any other feature that requires the presence of an ally.

These creatures can be polymorphed.

If you are using these creatures as sources for objects to become spell components, it seems on the face of it that you would be limited to one use only, because:

You can't have more than one familiar at a time. If you cast this spell while you already have a familiar, you instead cause it to adopt a new form.

and

You can't have more than one steed bonded by this spell at a time.

However, this depends on your DM's ruling about whether modifying the object counts as damage, and how damage to objects interacts with the true polymorph. This question asks whether polymorphing a creature into a twig and then breaking the twig in half would end the spell. This question assumes that if you polymorphed a creature into metal, you could melt the metal and reform it into numerous separate items without ending the spell.

Thus, depending on your DM's rulings, it might be possible to polymorph your familiar or steed into as large a single object of component as possible, and then divide the object, harvesting the pieces for use as multiple sets of components. The DM would then limit the number of times you could divide it before the object's hp reached zero and the spell was ended.

The object's size is limited by the size of the form of the creature:

Creature into Object. If you turn a creature into an object, it transforms along with whatever it is wearing and carrying into that form, as long as the object’s size is no larger than the creature’s size.

Since the limit is the original size, you will clearly get more from find steed here than you would from find familiar (and even more if you can cast find greater steed). However, note that the limit is size, not value. Even a size small familiar, polymorphed into a solid block of diamond, might be mined for numerous component gemstones with gem-cutter's tools or the fabricate spell.