What does a Simulacrum know?

Question

Somewhat a follow up to this question, when one creates a simulacrum, it obviously has to know some things (language, basic motor skills, complex motor skills needed to act in combat). It also has the statistics of the original. But would it have the information that the original has?

A practical example:

The party is tracking down a cult; they manage to capture (and prevent the suicide of) a cultist. They ask the cultist where the HQ is, but the cultist refuses to answer. Could the party make a simulacrum of the cultist and then ask the simulacrum the location of the cult's secret HQ and expect it to be able to answer it? Then could the simulacrum also be used to sneak into the HQ as a convincing double agent?

The question restated is: "Would a simulacrum know enough to imitate the original target effectively, or answer questions only the original target would know but the caster would not?"

Answer 1

No.

Trivially, the spell text does not say that a simulacrum knows what its "original" knows. Spells only do what they say they do, so the simulacrum doesn't know what the original knows.

For instance, the Clone spell explicitly states that the soul-infused clone keeps its memories (emphasis added):

The clone is physically identical to the original and has the same personality, memories, and abilities, but none of the original’s equipment.

Simulacrum does not have this language, so it doesn't retain its memories. It's also worth noting that this text delineates between three key aspects of a character: personality, memories, and abilities. While a simulacrum might know just enough to use its abilities, as detailed by its game statistics, it would not have memories like the location of the cult's secret HQ.

Other support:

It's not specifically stated in the spell, but the wording of the spell suggests that the simulacrum is a different creature that has the same game statistics and appearance as the original.

Below, I've bolded the places in the spell that show how the duplicate is different from the original:

You shape an illusory duplicate of one beast or humanoid that is within range for the entire Casting Time of the spell. 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.

Thus, the simulacrum has the appearance of the original creature, but nothing else.

Moreover, just because two creatures have the same game statistics doesn't mean they have the same knowledge--you can have two wizards that have the same stats but different knowledge, for example.

As for spells, as you point out, the text refers to expended spell slots, which seems to assume that the simulacrum does keep the spellcasting class feature of its original.

Answer 2

Tentative yes:

The 5e PhB provides limited clues about this question. It is stated that a simulacrum:

never increases its level or other abilities, nor can it regain expended spell slots

This implies that the simulacrum has spellcasting abilities or levels similar to (or at the same rank as) the original creature. Given that spellcasting abilities and class features require a lot of training, it would be reasonable to assume that the simulacrum also has basic memories of the target creature as well.

If we look at earlier editions for guidance, here is what we can learn from the 2e PhB, which has essentially the same spell with some differences. The 2e version is also of 7th level, it also creates the duplicate from snow and ice, it also states that the simulacrum has about half the original's hit points and 100 gp is required to fix each lost hit point. But according to the 2e version, the simulacrum is zombie-like and requires a reincarnation spell to obtain an actual vital force, and a limited wish spell to duplicate 40-65% of the original's knowledge and personality. Given that no such details are listed in the 5e edition version, but levels and spells are mentioned without the need for the casting of any extra spells, it might be reasonable to assume that the 5e simulacrum does automatically have about half (or more) of the knowledge of the original creature and could act as a double agent in a limited fashion.

Please note that the following tweets by Jeremy Crawford and Chris Perkins can also be read for guidance, and seem to support the arguments outlined above.

• Simulacra can use legendary actions of legendary creatures. https://twitter.com/JeremyECrawford/status/524704327944765441
• A simulacrum can even cast wish spells, if they are of the adequate level. https://twitter.com/ChrisPerkinsDnD/status/765574731554664449
• Simulacra cannot learn game abilities, but otherwise can function normally. https://twitter.com/JeremyECrawford/status/652557496888852480

Finally, please note that the twitter thread that follows the last item listed has a sentence:

It's up to your DM how much the simulacrum can do while abiding by the limitations set by the spell.

Answer 3

Everything

When it says duplicate, it means duplicate. The spell wouldn't be very useful at its intended use cases (creating a flawless infiltrator to replace a victim / having someone just as competent as yourself to see to the dull work you're too busy and important to do) if the simulacrum lacked the original's full memories, knowledge, and personality quirks.

A simulacrum can make the same Wisdom (Nature) checks and Intelligence (Arcana) checks that the original could, it has the same proficiencies and, implicitly, the same knowledge base and memories of where and how its original learned those facts. It can recognize creatures it has never met but that its original has memories of, and, aside from its absolute loyalty to its creator, it can behave in a manner completely consistent with how the original behaved. The fact that the illusory duplicate possesses these properties is made use of in multiple official adventures!

From the 2018 adventure Waterdeep: Dragon Heist, in chapter 8, "Winter Wizardry":

Secret Simulacrum
If the characters make an enemy of Manshoon, he tries to capture one of them and replace that character with a magical duplicate created using the simulacrum spell. If one of the players is absent for a game session and circumstances allow it, Manshoon targets that character for replacement while the rest of the party is distracted by other matters. You don't need to roleplay the character's capture; just assume it happens.

In the 2020 adventure Icewind Dale: Rime of the Frostmaiden, a simulacrum of a dead wizard shares gossip about wizard-peers that its creator knew and disliked:

The quest in Easthaven begins at the same time as the burning of the Red Wizard, Dzaan, who is described in the "Arcane Brotherhood" section of appendix C. Whether the characters are starting the adventure in Easthaven or have just arrived, they are present during Dzaan's fiery execution. They're too late to save Dzaan, but they might encounter a magical copy of him again in chapter 2 (see "Lost Spire of Netheril").
"Vellynne Harpell is a human necromancer, as cold and uncaring as the corpses she animates. She's a withered old fool whose greatest asset—her family name—does her no good in Icewind Dale."
The simulacrum, which looks and acts like Dzaan, has half of Dzaan's hit points and can't regain expended spell slots.
The sunken Netherese tower contains a special room that can transform the simulacrum into a real person—or any magical illusion into the real thing, for that matter. If this change occurs, the simulacrum effectively becomes a clone of Dzaan, authentic in every way.

In the level 10 adventure from the 2023 book Keys from the Golden Vault, "Party at Paliset Hall," the one flaw in a simulacrum's impersonation is the result of its loyalty to its evil creator:

A few days ago, unaware of the danger, Zorhanna donned the shard solitaire necklace to see how it looked with a new gown she planned to wear at the gala. Zorhanna's close contact with the necklace allowed the Far Realm entity to trap her inside the diamond. The entity then replaced Zorhanna with a simulacrum using one of the shard solitaire's magical properties. Zorhanna's simulacrum now wanders Paliset Hall, preparing for the arrival of the gala's guests, while the real Zorhanna remains trapped inside the shard solitaire.
Eliphas knows the following pieces of information:
Zorhanna's Simulacrum. "I'm now convinced that my wife has been replaced by a simulacrum—a lookalike invested with her knowledge and spellcasting ability. I dimly recall Zorhanna mentioning that the shard solitaire has the power to create such a thing."

Answer 4

Based on clarification by Jeremy Crawford himself, I'd say that this would be a definitive Yes.

A simulacrum is a duplicate of another creature at the time of the spell's casting. You essentially take a snapshot of that creature's game statistics at the completion of the 12-hour casting, and those become the statistics of the simulacrum. #DnD https://t.co/vupGQPmPEX — Jeremy Crawford (@JeremyECrawford) June 25, 2018

Since Jeremy Crawford said that a simulacrum is essentially a duplicate of the target at the time of casting, I'd say that a simulacrum would know everything the original knew at the time of casting.

Answer 5

No, and you probably would need a wish to make it happen...

The interpretation of the rules by Icyfire are dead on spot. The simulacrum does not have any memories or knowledge (apart from the general stuff that the proficiencies would give) of the original.

And it was as such during almost all editions of D&D.

In AD&D 2e, it was specifically stated in the spell description:

(...) a limited wish spell must be used to empower the duplicate with
40% to 65% (35% + 1d6 * 5%)
of the knowledge and personality of the original (...)

5e does not have limited wish, so as a last resort a wish to endow the simulacrum with the memories of the original could work depending on the DM approval.

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If it were in my game, I'd allow such a wish on one condition (apart from the whole stress and 33%'s):

• (unless willing) The original creature fails a saving throw (maybe Intelligence) against the 9th level spell (wish). The magic would scan its brain for precious information, so allowing a saving throw is very fair.