Is a simulacrum capable of breastfeeding?

Question

My friends and I made a bet that a Simulacrum is not capable of breastfeeding. My friend's character is married to a wizard, and in the discussion of how magic could be applied in family life, the topic of a simulacrum taking the place of the mother came up.

RAW there is nothing that says that a simulacrum is incapable of performing normal bodily functions

The duplicate is a creature, partially real and formed from ice or snow, and it can take actions and otherwise be affected as a normal creature. It appears to be the same as the original, but it has half the creature's hit point maximum and is formed without any equipment.

However, I feel it would be problematic if simulacrums were capable of, for example, siring children - which is the topic of a separate question.

Are there restrictions on the biological functions of a simulacrum that would prevent it from breastfeeding?

Answer 1

There is no restriction that forbids breastfeeding

Simulacrum states:

The duplicate is a creature, partially real and formed from ice or snow, and it can take actions and otherwise be affected as a normal creature. It appears to be the same as the original, but it has half the creature's hit point maximum and is formed without any equipment. Otherwise, the illusion uses all the statistics of the creature it duplicates, except that it is a construct.

Nothing there indicates that it would behave different from the creature it copies for normal biological functions like eating or breastfeeding. To the contrary, it can take actions as a normal creature, and uses all the statistics of the creature. (Otherwise, it also would be difficult for the simulacrum to present itself as the creature it copies in many social contexts.)

The simulacrum is a construct. There are few general rules for creature types, and there is no general rule that constructs do not need to breathe, eat, sleep or perform other biological functions. Simulacrum does not say it does not need to eat or sleep, so it must perform these normal bodily functions, just like the original creature (unless that one does not need to), and the same is consequently to be expected for other biological functions.

As a special case, it is ambiguous if the simulacrum can procreate, although the majority consensus on the question you link is that it cannot. If your DM decides it cannot, you might need to create a simulacrum of a creature that is already lactating, else the simulacrum would have no way to become pregnant and produce milk, which is necessary for breast feeding. (Of course that leaves the question of what happens to the unborn child, but as the spell only creates a copy of one creature, presumably it would not also be copied. Would lactation continue then? At that stage we are probably at the biology version of D&D is not a physics simulation, and likewise defer to the DM.)

There is one additional restriction on simulacrum that we need to discuss:

The simulacrum lacks the ability to learn or become more powerful, so it never increases its level or other abilities, nor can it regain expended spell slots.

Neither of these seems to preclude using normal biological functions, either. Designer intent is that the simulacrum loses all abilities and features that are limited in use, but the ability to breastfeed is not a class feature, and the rules text also does not enforce this, so technically this is not an obstacle either.

Always keep in mind that your DM has the last word on how they run certain game features, which is especially relevant for broken and insufficiently defined ones like simulacrum.

Answer 2

How we homeruled this

In one of our campaigns, I played a wizard who used simulacrum, using it from 13th level, through 20th. My wizard pretty much always had a simulacrum.

Simulacrum is a challenging spell, just look at how many posts there are about it here. Many questions relate to biological functions.

We made a series of houserules, and one of them was a general rule that covers a sim's biology.

Our rule:

• The sim is a magical construct. It appears to be alive, and can be killed, but its life is but an illusion, sustained by magic. It is not a biological creature, but a magical one. Cut it, and it bleeds, but the blood does not keep it alive, magic does. It breathes, and without air it dies, but magic keeps it alive, not air. It requires food and water, but they do not sustain its body, only the illusion.

Like many houserules, it made perfect sense to us, but reading it, I'm not sure it's application here is completely obvious. Our intent was that it is magic, not biology, and it suffers all the pitfalls of being alive, but it is not, it is an illusion.

As an example, we found out that mind flayers considered the sim a perfectly valid target (terrifying, watching a mind flayer go after your very very expensive, more than doubly-squishy toy), and while we (fortunately) did not find out if mind flayers found sim brains nourishing, I asked the DM about it later. They said, my wizard was fairly sure, according to research previously conducted, that a mind flayer would be happy to eat the brain, but since it is an illusion, not a real brain, the mind flayer would find it unsatisfactory and would gain at best some momentarily illusion of nourishment.

We never addressed the question of breastfeeding directly, but looking at similar issues that we did address, such as does the brain nourish a mind flayer, the answer would have been that the sim of a lactating creature would produce milk, but since the milk is an illusion, not real milk, a nursing infant would find it unsatisfactory and would gain at best some momentarily illusion of nourishment.

We also ruled that the sim was not renewable, any resource that it had that would normally be renewed over time, was only usable once. So a nursing sim would provide unsatisfactory and illusory milk once, then nevermore.

Conclusion

Simulacrum is a deeply intriguing spell, but it leaves a lot unspecified. The RAW can be poked at, but our experience was that no amount of RAW examination made the spell playable, but that our houserules did. Any DM might reasonably rule differently from what I provided here, but this is what worked for us.

Answer 3

This answer is based on experience in play.

The wet nurse / simulacrum fed my bard's baby

But it could not give birth.

Simulacrum and world building concerns

Near the end of our 1-20 campaign a few years ago my bard got both wish and simulacrum as magical secrets. Our sorcerer / warlock was engaged in a power struggle for the Serpent Throne (in that game world). It was my intention, expressed to the DM, to have my bard (female) conceive a child with the sorcerer / warlock (male) and then make three simulacra who would (within the next game year) give birth to three heirs while my bard gave birth to the fourth. Why?
We expected various assassination attempts once he gained the throne and I wanted him to have multiple heirs stashed around various corners of the world, and fostered by some of the nobles with whom we were allied.

The DM ruled that mechanically this could work, but a world building problem arose: each child needed a soul, and he wasn't comfortable with PCs creating souls in that manner. Soul creation was within the purview of various deities and demigods, powers, etc. in his game world.
Therefore, this would not work - the simulacra would not / could not gestate and then give birth to a child. We abandoned that plan and I used wish to clone the Warlock/Sorcerer.
The above is an example of an in-game or in-world restriction on what simulacrum can and cannot do based on the DM's world building scheme.

We applied "construct" more than the "illusion" of Jack's answer.

My bard mated with an ancient golden dragon (change shape for the win!) and gave birth to a child. She created a simulacrum almost immediately after she had begun breastfeeding. I approached that topic - now that my bard is lactating, will the sim be able to do the same? - and the DM ruled "Yes, that made sense from a mechanical perspective." It didn't upset his general world building scheme. (This answer covers some mechanical considerations).

This allowed my bard to sometimes go off and do things while the wet nurse took care of the baby during the closing stages of the campaign.

The spell leaves a lot unspecified...

... so you have to fill in the blanks at the table with the world builder. As we explored the spell (and its various loopholes) we arrived at a table-level equilibrium for what it does and doesn't do.

• In our case, only one Sim at a time, period, was the DMs restriction.

  • The DM doesn't like the "cheese" factor of the loophole that allows multiple copies to be made. (Fine with me, since I'd have to manage all that).

• No spell slot regeneration and no short rest ability regeneration (hit dice, bardic inspiration, etc).

This left the bard sim still able to do many useful things, to include:

1. Sing all songs and play all instruments, which meant that some of my bard's performances were duets (Dueling citterns...)
2. Use various cantrips (minor illusion to entertain the kids at a party)
3. Train sailors on our ships to use simple weapons and short swords / rapiers (which bards are proficient in)
4. Be visually present to indicate where my bard was (not really) when my bard put on her amulet of non-detection and went elsewhere in the world.
5. Get True Polymorphed into an adult Emerald or Gold dragon now and again when my bard needed to do something on dragon back. That change in form was limited to the one-hour concentration. DM ruled that a "permanent" change into an adult dragon would need a soul and that wasn't going to fit his world building as discussed above.
6. In extremis, cast a known spell (but the slot can't be recovered)

Work together at the table to fit simulacrum into the world

As the first answer points out there's no explicit restriction - the sim probably can. Our experience was that it was important to work with the DM on the specifics to make sure that simulacrum fits into the themes and constraints of that particular imaginary world as built by that DM (or the table, if player input into world building is a thing at a given table). A DM could lean into the illusion piece, as Jack's table did, and the breast milk would not actually provide nourishment. That makes sense as well.