Can a tiny mimic turn into a magic sword?

Question

In a manga I read recently, a nobleman had ruled his town diligently with the aid of a "Holy Sword" that was written so beautifully as a Blackrazer, having installed a bloodlust in their host through corruption. However, when the nobleman was later defeated by the hero and the church, the sword cackled, ate his wielder's soul, and turned into a large mimic (well fed with all the people that nobleman would secretly slaughter).

While this scene is written beautifully as an encounter that the DM might use, I was more curious about how closely the mechanics would match the lore of the Hexlock; a Tiny Mimic Sidekick (thanks to Tasha's) who was perhaps a spellbook in a previous bond, making a pact with the character, promising to be their sword and to teach them the power of hexes in exchange for constant sacrifices of blood.

So far, I forsee no RAW or RAI issues if the mimic takes the form of a mundane sword, (one could class it under fluff or relfavouring), but I was wondering if they could later take on the properties of magical swords when the party would otherwise upgrade anyways?

Answer 1

By the rules, a mimic wouldn't make a good sword.

The relevant abilities of a mimic are the following:

Shapechanger. The mimic can use its action to polymorph into an object or back into its true, amorphous form. Its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Adhesive (Object Form Only). The mimic adheres to anything that touches it. A Huge or smaller creature adhered to the mimic is also grappled by it (escape DC 13). Ability checks made to escape this grapple have disadvantage.

False Appearance (Object Form Only). While the mimic remains motionless, it is indistinguishable from an ordinary object.

So indeed, a mimic could use Shapechanger to take the appearance of a sword, but because "Its statistics are the same in each form" it wouldn't get the hardness of steel nor the sharpness of a blade.

Also, that adhesive isn't optional: someone wielding that mimic sword would get grappled every time whatever the agreement they may have with the mimic.

Now you could of course ditch those rules and homebrew something to make your cool mimic-sidekick idea work, like a subspecies of smaller mimics who are smarter and do actually take the properties of the mundane materials they shapechange into.

Answer 2

Homebrew use is up to the DM.

The Sidekick rules in Tasha’s Cauldron do permit a Juvenile Mimic to be your sidekick, since it is CR 0:

A sidekick can be any type of creature with a stat block in the Monster Manual or another D&D book, but the challenge rating in its stat block must be 1/2 or lower.

However, everything else you describe in the question is outside the realm of the printed rules for sidekicks. Using your sidekick as a weapon and having your sidekick gain mundane or magical properties not described in its statblock or the sidekick features is homebrew. And the DM decides what homebrew features to permit at the table.

Answer 3

RAW, but underpowered and likely boring

As Thomas Markov suggests, start with a CR0 Juvenile Mimic using the Sidekick rules from TCoE.

A sidekick can be any type of creature with a stat block in the Monster Manual or another D&D book, but the challenge rating in its stat block must be 1/2 or lower.

Then, level up the juvenile mimic as you level:

Whenever a group's average level goes up, the sidekick gains a level...it gains one Hit Die, and its hit point maximum increases.

Level it as a warrior sidekick. All of the abilities will be useful, but you will get the most mileage from martial role (1st, defender), improved critical (3rd), ASI (4th and 8th - all to Dex), Extra Attack, and Battle Readiness. As a note about the ASI, you can't do much with its Str 1 by the Sidekick rules, but you can start at Dex 12 (juvenile) and, as the juvenile does, use its bite attack based on Dex rather than Str, increasing its to-hit with each 2-point Dex boost.

Note that the juvenile mimic does not have the Adhesive of an adult mimic, so you don't need to worry about it sticking to things or things sticking to it.

When you draw the mimic from its sheath, it at first looks like smooth, sharp steel sword (false appearance). But then, during the round you are casting your defensive spell in preparation for combat, it uses its shape-shift to become a type of rere, a sword covered in teeth - and dripping with acid. Then, when the mimic attacks, it uses its Bite, doing piercing and acid damage.

As far as the hexlock, you simply take the Help action each turn, granting the mimic advantage on the first of its next attacks:

Alternatively, you can aid a friendly creature in attacking a creature within 5 feet of you. You feint, distract the target, or in some other way team up to make your ally's attack more effective. If your ally attacks the target before your next turn, the first attack roll is made with advantage.

The "some other way" you team up with the mimic is by wielding it as a sword while the mimic makes its bite attacks. That doesn't give your hexlock a lot to do, since you are constantly sacrificing your main action to help your sword sidekick attack, so you would need to be pretty invested in the concept. You can focus on defensive spells like shield, false life (with fiendish vigor), armor of agathys and so forth, but all your hex powers will be underutilized since it will be the mimic who is damaging things, not you, and the mimic can't be your pact weapon, so the invocations that synergize with your pact weapon will be of little utility. It would be great if you had an attack as a bonus action, but that's a pretty limited option RAW. To some extent you would be playing the sidekick as your character, and using your actual PC as the vehicle to level up and create abilities for the sidekick to use. Thus your hexlock themselves would be greatly sub-optimized and underplayed, and might not be fun unless you are into that or everyone in your party had similarly disadvantaged character concepts.

One strategy might be to invest heavily in the invocations that enhance your eldritch blast, use this at a distance, and only use the mimic when you stumble into melee - but that wastes your selection of subclass as hexblade. Another possibility would be to have your pact weapon be a throwing weapon that you could wield in one hand while holding the mimic in the other, and invest your invocations in things that will buff your thrown pact weapon as you move between thrown weapon and melee weapon range.

Making the mimic magical, and having it devour souls would be strictly homebrew, though.

Answer 4

I see one glaring problem with a mimic-sword. As has been discussed it doesn't gain the properties of a sword.

For wielding it, sure, you could swing a mimic-sword, but I would treat it as a club for damage. The real problem is the mimic isn't metal, I would consider it to take the same damage as it inflicts. You're basically picking up a creature and bashing it on things.

Answer 5

A mimic sword can be fun, but makes a bad patron

Rules-wise, the statistics of a minic stay the same no matter what form it takes, so it could not be a real magic sword, and anything beyond that is up to the DM.

A tiny mimic does not fit at all with the concept of a warlock patron. Patrons are otherwirldly beings, and a mimic is not:

A warlock is defined by a pact with an otherworldly being.

Patrons are supposed to be extremely powerful entities, like

a demon prince, an archdevil, or an utterly alien entity

and even a fully grown minic is a mere CR2. Also, as the patron provides all powers to the warlock, what would happen if someone killed it, which is not that hard? There's a reason the patron is an off-screen entity, that cannot really be attacked.

That said, if what you really want is fun with a mimic sword, I want to add an experience based answer here. We play a campaign that has a magic items, but we are not exactly showered in them. For the two martial characters in our group, where magic weapons matter most, it took us deep into tier two until both had bona fide magic weapons.

In the interim time, our paladin was able to acquire a special mimic that could turn into a sword at the local temple of Gond that sells mechanic wonders snd inventions. Here it is:

Toothy the Trusty Mimic

Wondrous item, rare (requires attunement)

Toothy is a tame mimic created in an age long past by a powerful wizard as a gift for a warrior companion.

Sentience. Toothy is a sentient neutral weapon with an Intelligence of 6, a Wisdom of 13, and a Charisma of 8. It has hearing and darkvision out to a range of 60 feet. Toothy can speak, read, and understand Common. Its voice is wet and gurgly.

Personality. Toothy is simple-minded, and primarily interested in eating. So long as Toothy believes its wielder will provide it with an ample supply of raw meat, it will gladly follow its wielder's orders. If Toothy goes three or more days without being fed any raw meat, a conflict between it and its wielder occurs at the next sunset.

Shapechanger. While attuned to this item, you can use an action to command it to change its form to one of the following options:

Weapon. Toothy transforms into a simple or martial melee weapon of your choice. You are considered proficient with the weapon if you were not already. When you hit a Large or smaller target with Toothy while it is in this form, you can use a bonus action to attempt to restrain the target. The target must succeed on a DC 15 Strength saving throw or be restrained. The target can re-attempt the saving throw as an action, ending the effect on itself on a success. While Toothy has a target restrained in this way, it cannot be used to make attack rolls against any other targets. You can command Toothy to release a restrained creature at any time without requiring an action.

Shield. Toothy transforms into a shield. You are considered proficient with the shield if you were not already. When a Large or smaller creature misses you with a melee attack while Toothy is in this form, you can use your reaction to attempt to restrain the target. The target must succeed on a DC 15 Strength saving throw or be restrained. The creature can re-attempt the saving throw as an action, ending the effect on itself on a success. While Toothy has a creature restrained in this way, it provides no bonus to your AC. You can command Toothy to release a restrained creature at any time without requiring an action.

Other Item. Toothy takes the form of any nonmagical object no larger than Medium and worth no more than 100 GP. Toothy can transform into a duplicate of a nonmagical object, such as a key, if you possess the original for Toothy to use as a reference.

He mostly used it as a weapon, with a few side uses as an object. It really worked like a magic item, with attunement. It also provided special tactical options, like restraining opponents, which made for some interesting choices in combat and fit to the normal mimic's abilities. It needed to be fed, so he was buying meat for it. And in a few occasions, it came in handy as a ladder or similar, so he did not have to lug around as much equipment.