What are the rules for making constructs other than golems?

Question

If a PC wants to make a golem specifically, the various Manuals of Golems have them covered. That's pretty clear in the rules (Dungeon Master's Guide, page 180).

However, there don't appear to be many rules for how a PC can create constructs other than golems, such as animated suits of armor. (Page 129 of the Dungeon Master's Guide talks about how much material, time, and money is needed for magic items of known ratings - common, uncommon, rare, very rare, and legendary. However it is not clear whether animated suits of armor are "common," and possibly each Dungeon Master is supposed to make a campaign-specific ruling.)

(Animate Object lasts only 1 minute. Obviously a construct should be more-or-less permanent, and I'm used to how other editions handle converting temporary effects into permanent ones via a permanency spell or something similar, but permanency doesn't appear to be in 5e.)

So how is someone supposed to create constructs other than golems? The Animated Objects entry in the Monster Manual (p. 19) says:

Animated objects are crafted with potent magic to follow the commands of their creators.

Where are the rules for this potent magic? Does the game just leave it up to DMs to to define this "potent magic" via homebrewed rituals, new Manuals types, and whatnot?

Answer 1

The manual of golems (DMG, p. 180) requires its reader to possess at least two 5th-level spell slots, the same as the 5th-level slot to cast animate objects.

I know no other spell that could turn armor into an animated armor. I asked myself why would someone with access to 5th-level spells would try to get a CR 1 animated armor when he could get a CR 9 clay golem.

Since this seems like a significantly less powerful use case, if you wanted to house-rule it, you could allow a manual of animated objects that only requires one 5th-level slot and would be a rare magic item (instead of very rare).

Answer 2

The artificer class (officially released in 2019) lets you get a permanent animated suit of armor, or two.

At level 2, the artificer class gets the Infuse Item feature. One of the infusions they can choose is the Homunculus Servant infusion (TCoE, p. 21-22; E:RftLW, p. 62); with a gem or crystal worth 100 gp, they can create a Tiny construct that can even fly:

You determine the homunculus's appearance. Some artificers prefer mechanical-looking birds, whereas some like winged vials or miniature, animate cauldrons.

In addition, at level 3, the artificer gets the Artificer Specialist feature, letting them choose their subclass. The Battle Smith subclass gets the Steel Defender feature (TCoE, p. 19; E:RftLW, p. 61), letting them create a Medium construct that is ostensibly made of metal:

Your tinkering has borne you a faithful companion, a steel defender. It's friendly to you and your companions, and it obeys your commands. [...] You determine the creature's appearance and whether it has two legs or four; your choice has no effect on its game statistics.

Answer 3

Short Answer: yes, is up to the DM to decide what kind of potent magic or Manuals are needed to create anything different than the listed Golems

Long Answer: The definiton of the Golems states that "...the golem's creator infuses it with a spirit from the Elemental Plane of Earth." so ,in the specific case of the animated armor, I would let the PCs to create minor constructs like that since the moment they can cast Conjure Minor Elementals as far as they have a manual for it.

Personally with the Crawling Claw and the Homunculus (both CR 0) I would let the PCs create them since level 5 or so....as far as they can get the hands on the specific manual or get the knowledge from some powerful being (either option would be a source of adventures on its own)

With more problematic constructs like the Helmet Horror or the Shield Guardian, you can compare the CR of the construct with the CR of the creatures conjured with different spells to get an idea of the level that the PCs should have to create them, and/or take a look to the creation rules and requisites of D&D 3.0 or 3.5.

Answer 4

There are two spells in Xanathar's Guide to Everything that create constructs, although only one is permanent:

• Tiny servant¹ (XGtE, p. 168) is a 3rd-level wizard spell that makes a Tiny object (the illustration shows a beer mug) grow arms and legs and become a special construct creature - also called a tiny servant. The spell has no material components (consumed or otherwise), but only lasts for 8 hours. It takes 1 minute to cast the spell.
• Create homunculus¹ (XGtE, p. 152) is a 6th-level wizard spell that permanently creates a loyal homunculus creature. The spell consumes clay, ash, and mandrake root, no price specified; but it demands that the wizard cut themselves with a jeweled dagger (worth at least 1000 gp), doing 2d4 piercing damage and dripping the blood from the wound on the other components to create a homunculus. A wizard can only have one homunculus at a time. The spell takes 1 hour to cast, but the homunculus remains animated until it dies (or you do).

¹ The linked pages will only be accessible if you own Xanathar's Guide to Everything on D&D Beyond.