The Astral Plane is a vast, ever-present dimension that your party can wind up in no matter what campaign you're playing. The upcoming Spelljammer: Adventures in Space books use the Astral Plane as a set piece for rollicking, spacefaring adventures, but its uses don't stop there. The Astral Plane is an ever-present way of traveling to the Outer Planes, so whether you're off to the glorious plane of Mount Celestia to beseech the gods for their aid or the grim plane of Hades to rescue the damned soul of a companion, you'll likely need a way to get there. That's where the Astral Plane comes in.

While those that venture into the Astral Plane won't need to worry about food or oxygen, the plane is far from hospitable. Dangerous creatures roam the expanse of the Astral Plane's silvery seas, one of the more fearsome of which is the gargantuan astral dreadnought, an ancient monstrosity of insatiable hunger. 

This article will cover everything you need to know before unleashing this terrifying beast on your party.

• What Are Astral Dreadnoughts? 
• How Astral Dreadnoughts Hunt Their Prey 
• Playing With Astral Dreadnoughts at Your Table 

The Astral Plane

The Astral Plane is a boundless realm of thought and dream that has existed in Dungeons & Dragons since the first edition. To learn more about exploring this dream-like realm, see the Astral Plane section under "Creating a Multiverse" in the Dungeon Master's Guide.

What Are Astral Dreadnoughts? 

Astral dreadnoughts have stalked the Astral Plane since the dawn of the multiverse. No one knows how these creatures first came into being, though some theorize that they were manifested by a god of the Outer Planes who wanted to prevent incursion from the Astral Plane. 

At roughly the same size as an ancient red dragon, astral dreadnoughts are the apex predators of the Astral Plane. Beyond their formidable claws, razor-sharp teeth, and nearly impenetrable carapace, astral dreadnoughts have an innate connection to the Astral Plane that grants them extraordinary and frightening powers. 

Those that survive encounters with these monstrous creatures speak of the astral dreadnought's eye as one of its most potent weapons. Any creature that meets the gaze of the astral dreadnought will experience its mortality in the starry reflection of its eye. Because the astral dreadnought emits an antimagic field from its eye, the feeling of mortality is especially strong for spellcasters.

The Astral Dreadnought's Demiplanar Donjon

Those unlucky enough to be the victim of an astral dreadnought's feeding—if one survives the process of being swallowed—will find that being dissolved by stomach acid may be a better fate than the one awaiting them. You see, the "stomach" of an astral dreadnought is an extraplanar space called a Demiplanar Donjon. Anything eaten by the dreadnought is sent to this demiplane, where it remains for eternity (or until the dreadnought is killed). The demiplane operates differently from the Astral Plane as it has gravity, breathable air, and organic matter decays. This means that those who are swallowed and have no way of escaping will remain trapped until they die of starvation or dehydration. 

What Will You Find in an Astral Dreadnought's Donjon? 

If your party is planning on hunting an astral dreadnought, it would be apt to prepare for what they may find in its demiplane. To help get you started, roll on the table below for some ideas.

Demiplanar Donjon Contents

How Astral Dreadnoughts Hunt Their Prey 

The insatiable appetite of the astral dreadnought means that they are not picky about their prey. Astral dreadnoughts tend to eat anything they come across, which isn't much considering that the Astral Plane is mainly empty.

Astral dreadnoughts aren't particularly cunning creatures. These hulking monstrosities don't scheme or plot the demise of their prey. Instead, they use their overwhelming strength and size to incapacitate their prey, then proceed with their meal. One strategy the dreadnought has shown to possess is the ability to innately detect spellcasters. When a creature with magical capabilities is encountered, the astral dreadnought will focus its eye on the spellcaster to render their magic useless.

The astral dreadnought's primary concern in combat is how to keep the maximum number of creatures in its antimagic field while still being in range to attack. Its Bite has a range of 10 feet, and its Claws have a range of 20 feet, which allow it to maintain some distance. But, unfortunately for the astral dreadnought, its eye's antimagic field is conical. So even at 20 feet, the antimagic field will be significantly narrower than if the dreadnought were further away. 

A fight against an astral dreadnought may seem relatively straightforward to a party of adventurers. Stay out of reach, blind the eye, and don't get swallowed. This misconception will end abruptly for any characters using magic to project their form into the Astral Plane. The dreadnought's Sever Silver Cord trait allows it to cut a character's silver cord—automatically and instantly killing any creature using the astral projection—when it lands a critical hit.

Playing With Astral Dreadnoughts at Your Table 

Astral dreadnoughts are a foundational set piece for campaigns that travel into the Astral Plane. Hunting one of these deadly beasts could be how the party wins over a group of githyanki, or they could need to track and find the dreadnought that devoured a relic they need to acquire. In the vast, open emptiness of the Astral Plane, an astral dreadnought is a surefire way to provide a significant challenge to a high-level party.

The plot hook below is for parties at a high enough level to cast astral projection—or has some other way to get to the Astral Plane—and can defeat the CR 21 astral dreadnought.

The One That Got Away

"Aye, ya shoulda seen 'er. Twice the size o' my ship, pale as the moon, and that eye—oh gods, that eye—made me feel like I was staring into my grave it did. I did what any good captain would do and I turned tail and ran. Didn't matter. It caught us and killed me whole crew. Took me leg off at the knee, but I was able to blind it and get away. Turns me stomach thinkin' that beast is still floating out there digesting me crew.

The wizened githyanki captain shudders and drinks deeply from his mug. "Tell ye what, if you hunt it down and bring me back it's eye, I'll give ya what yer after."

The characters can meet the githyanki captain at an inn in a setting that provides access to the Astral Plane. Since Wildspace intersects with the Astral Sea, Spelljammer campaigns work particularly well here. Otherwise, extraplanar locations like Sigil or the City of Brass are an excellent place to start.

Once the characters have worked out their deal with the captain, he will tell them the general vicinity where he encountered the dreadnought. Whether or not you want to tell your players exactly what they're hunting is up to you.

Exploring the Astral Plane

Once the party reaches the Astral Plane, physically or by projecting their astral form, locating the astral dreadnought takes 1d4 × 10 hours of travel. For every 10 hours of travel, have the party roll on the encounter table below:

Big White

The astral dreadnought that attacked the githyanki captain has a pale white hide and a scar through its eye. Sneaking up on the dreadnought requires a DC 19 Dexterity (Stealth) check. When it sees the party, the dreadnought will focus on spellcasters with a vicious determination and will not attack martial characters until the spellcasters have been dealt with.

If the party needs to retreat or is losing the fight badly, allow them to make attacks specifically on the dreadnought's eye with the intent to blind it. The dreadnought's eye has AC 22 and immunity to psychic damage. If an attack lands, the dreadnought takes no damage but must succeed on a DC 15 Constitution saving throw or be blinded until the start of its next turn.

Defeating the Dreadnought

Once the dreadnought is defeated, allow the party to search the contents of its Demiplanar Donjon. The travel back to the githyanki captain can be as eventful as you wish, though parties using astral projection can end the spell with an action to return to their bodies without any further trouble.

Into the Belly of the Beast

The Astral Plane is a staple set piece for high-level, plane-hopping adventures. While it is a mainly empty means of traveling to the Outer Planes, it offers a unique landscape coupled with creatures that cannot be found anywhere else. Where will your next trip through the silvery sea take you? 

Mike Bernier (@arcane_eye) is the founder of Arcane Eye, a site focused on providing useful tips and tricks to all those involved in the world of D&D. Outside of writing for Arcane Eye, Mike spends most of his time playing games, hiking with his girlfriend, and tending the veritable jungle of houseplants that have invaded his house.