Nautiloid 5e: A Guide to the Mind Flayers’ Conch Ships

Nautiloids. The eldritch and ethereal blend of deep space and deep ocean, tentacles in dark protruding from a great curled shell, piloted by creatures just as alien as their ship.

These ships that travel the void between stars are the transport of the Mind Flayers, unbinding them from the terrestrial concerns of a single planet to feast on the minds of a thousand worlds.

Space travel is an undeniably fascinating and story-rich setting, but it’s difficult to blend well with high fantasy. No hobbit ever built a rocket ship in one of Tolkien’s tales, and that pretty much set the stage.

Tell that to D&D, though. Through the editions, D&D has found ways to tell its story in the outer reaches of the final frontier, and with the addition of the Spelljammer set, D&D 5e is no different.

While many species and empires have found ways to travel through the heavens, Nautiloids stand out for their deep-sea design with overtones of Lovecraft and the warning they represent:

The Mind Flayers are coming.

What Are the Nautiloids?

Nautiloids are a kind of spelljammer ship, magical craft created to cross the inter-planetary barrier. They look just like enormous nautilus shells, hence the name, but are remarkably better armed than the real-life sea creatures.

If you’re new to spelljammer ships or just to Nautiloids specifically, there are a few key features you’ll want to note,

Spelljammer Propulsion

Spelljammer ships are powered by magic, specifically a magical helm or chair installed into the ship that, when used by a spellcaster capable of controlling the vessel, powers propulsion and life support.

That’s fairly straightforward. What’s a little more complicated is the way spelljammer generally handles propulsion. While the set is still pretty new, it looks to work similarly to other spelljammer rules in the past.

That means that, like all spelljammer ships, Nautiloids have two modes of propulsion: one for atmospheric travel (travel on a planet) and one for travel through wildspace (D&D’s term for the vacuum of space).

This is extremely reasonable since spelljammer ships are capable of moving at relativistic speeds (speeds approaching the speed of light), and anything that tried to match that kind of velocity in an atmosphere would simply turn itself into a colorful smear of fire as it evaporated due to the heat from friction with air.

If you DM a spelljammer campaign, I strongly recommend that you make it impossible to use the relativistic mode in an atmosphere of any kind since where most people see the horrific destruction of rare magical artifacts and a high likelihood of death, your average D&D player sees only the potential to roll a truly unreasonable amount of damage die. Just say the magic doesn’t function so close to a planet, and the propulsion of Nautiloids, like all spelljammer ships, shouldn’t be an issue.


Unlike all spelljammer ships, Nautiloids are heavily organic. While we’ll get into details of the layout a little later, you should know that the inside of a Mind Flayer’s Nautiloid will be very fleshy. Instead of doors, there will be orifices that react to telepathy to open and shut. Instead of lightbulbs or torches, bioluminescent orbs will provide a constant, if dim, source of illumination.

Notably, while this organic aspect extends to the tentacles of the Nautiloid, the ship is not a living creature. The shell is harvested from some unknown animal before being used to make the ship; the organic components come from the process of shipbuilding and modifications made by the Mind Flayers to adapt the ship to their unique physiology.

The exact origins of Nautiloids are a bit of a mystery in 5e, (though check out some of the old lore from previous editions for more details), but it’s generally accepted that while Nautiloids almost always mean Mind Flayers, the Mind Flayers themselves are not the inventors of the ship and in fact no longer know the secret to creating new ones.

That makes each Nautiloid very special indeed for the brain-sucking creatures; Mind Flayers won’t give up a ship unless there’s really no choice, and as long as they’re in the ship, they will probably try to play it safe as far as the combat side of things goes.

The Nautiloid Class

While Nautiloid ships are very valuable and can represent a significant challenge to a mid-level party (what with all the Mind Flayers aboard), it’s important to note that Nautiloids are a lot more like small clippers than fully armed warships.

Spelljammer ships come in all shapes and sizes, and while it’s possible for there to be dreadnought class warships filled with legions of Mind Flayers and their servitors, Nautiloids are not that. In fact, a given Nautiloid will only hold about 20-30 people, most of whom are slaves or servitors of the Mind Flayers. This translates to a tonnage of 35 tons, roughly half of which is suitable for cargo. For comparison, modern-day ships can have tonnages of hundreds of thousands of tons.

Anatomy of a Spaceship

Nautiloid ships can be variably designed. While a few key features will be omnipresent, the details of each room are mostly up to the DM (or the campaign they’re running!) That said, if you do want specific details, you can find a nice layout of the various decks here.

Generally, Nautiloids have a series of stacked decks in the shell of the ship along with a ram at the end and tentacles that can grab potential prisoners and/or food for the Mind Flayers inside. It’s also typical to have at least one open combat deck armed with ballistae and catapults for when ship-to-ship combat is needed.

The decks below the surface of the ship are usually filled with prisoners, cargo, and occasionally the strange creatures that Mind Flayers use as servants. These are shadowy areas lit by bioluminescent orbs but not well enough that sight is clear and easy.

The Mind Flayers themselves will live within the shell of the Nautiloid. There, protected from the harsh radiation of space, they control the ship via the magical helm (usually attuned to the specific telepathic signature of a Mind Flayer and nothing else).

The exact deck that houses the command center and the helm that allows the Nautiloid to travel the stars is really up to you. Placing it at the top makes it more easily exposed to heavy fire but also makes it harder for infiltrators to reach, so the exact position will have tactical tradeoffs regardless.

Other than the command deck, battle deck, and living quarters, you may also want to provide an area for scouting. From this position, the crew of the Nautiloid will be able to chart direction and spot incoming threats, either through tools or with their own eyes. However, it is not an essential deck to have since the battle deck can also serve this purpose.

From this simple structure, it is of course possible to expand. You might decide to simply make the Nautiloid bigger or add additional features such as smaller fighters or advanced weaponry. However, as long as you build on the core ship described here, you’ll have something that remains true to what a Nautiloid is: a ship like an enormous sea creature, drifting through space, wielding tentacles, and carrying an enormous protective shell that houses monsters.

Spelljammer Adventures: On Earth as They Are in the Heavens

Running an adventure or even a campaign with Nautiloids in it can take one of two basic forms. Either your players encounter a Nautiloid on their home planet, or they venture into the stars only to find mind-eating horrors awaiting them. You could also do both.

Either way, the choice of environment will heavily influence how an encounter or campaign featuring Nautiloids plays out. Nautiloids on the ground, so to speak, will serve as quick-moving transport that easily outmaneuvers the players and represents a massive potential gain if they can capture it while functional. A downed Nautiloid can also stir a great deal of plot as the Mind Flayers inside won’t be picky about how they go about repairing its organic parts.

Remember that Nautiloids are highly valued by Mind Flayers and are extremely rare. This might manifest as extreme caution or an intense willingness to fight off potential thieves, but it will manifest.

On the other hand, Nautiloids faced by the party in space will exist on more even terms. Here one should probably take inspiration from naval battles or naval pursuits should our heroes be less well equipped than a Nautiloid. With the magic of spelljammer ships to protect them, boarding parties are a very real possibility for both sides.

Moreover, you should consider what would happen if the party’s spelljammer ship was damaged beyond their ability to repair it in deep space. These ships are intensely powerful magical constructions, but they do have a limited amount of air, food, and water. Make sure everyone understands the risks (out of character) of space travel.

If you’re still looking for inspiration and don’t yet have the new books from Wizards of the Coast, consider trying to find a copy of Icewind Dale – Rime of the Frostmaiden. This adventure is mostly unrelated to spelljammer ships and Nautiloids, but players can encounter a downed Nautiloid in the frozen North.

If you need inspiration or just want some hard-and-fast rules to lean on, there are several excellent pieces of information there about the layout of Nautiloid ships, how much damage the self-destruct does, and what kinds of creatures a downed Nautiloid ship might be hiding.

Final Thoughts

Mind Flayers are fascinating foes. Their eldritch look, mysterious powers, and hive mind make them one of D&D’s most iconic monsters. And Nautiloids are the natural step up. These flying ships can be terrifying when you’re on the ground and a formidable foe even when you have a ship of your own.

We’ve looked at what these ships are, how they work, and the stories they can be a part of, but if there’s one thing you should take away from this article about running Nautiloids in your campaign, it’s to lean into the eldritch horror of it all.

If you have a downed Nautiloid that your players have entered, play up the weirdness of an organic spaceship. If your players are in space, take advantage of the utter silence out there… and the fact that Mind Flayers can coordinate with their telepathy in perfect silence.

However you decide to use Nautiloids, as long as you take advantage of the weirdness of a massive flying nautilus shell, you’ll be able to create a memorable and fun story.