Once long ago, Spacefarers managed to break into the vast vacuum of Phlogiston. They sailed from one Crystal Sphere to the next, piloting Spelljammer vessels to fare the most ominous regions of the Material Plane. Such vessels took the appearance of seafaring galleons, giant weaponry, holy symbols, monsters, insects and animals. They were operated by users of Spelljammer magic, which also afforded mortal creatures the ability to breathe in the climate of all-encompassing, enigmatic, and delicately flammable Phlogiston. Of benevolent or crude intention, every sort of Spelljammer faced a myriad of other vagrants on their voyages. Such was a natural effect of the Phlogiston rivers that streamed from one Crystal Sphere to the next. To venture beyond the rivers was most often an act of great ignorance to what lies ahead for any wayward Spelljammer. Populated by nightmarish fiends, the vast expanse beyond the rivers was mostly uncharted by mortal kind.

After the mysterious events of the Omniglow, the Phlogiston was rendered totally inaccessible to mortal creatures for centuries. Developments in Spelljammer technology were not yielded, however, and were taken up in wait by the many Artificers and Cosmic Sages dedicated to their trade. After decades of patience, such laborers revered the discovery of commutable Phlogiston near Realmspace. Within years, the Trans-Spacial Union of Astroficers was born with an ethos to revive the practice of Spelljammer-travel. Now, the Phlogiston is reforming, and the studious Sages of the multiverse are taking steps toward the edges of Wildspace once again.

Mystic Vessel

You are fascinated with vessels and vehicles. You’ve always found that they make travel easier and way, way, way cooler. Naturally, you have a vessel of your own, with a design chosen by you and an intimate familiarity that allows you to use the vehicle in standard combat at the cost of one unoccupied hand.

Your vessel has its own hit points which, once exhausted, mechanically destroy the vessel. You are able to perform repairs on your vessel with Tinker’s Tools using the Perform Maintenance action.

During combat, you may also drive your vehicle directly into enemies with the Ram action, at the cost of some of your vessel’s hit points (1d12 per enemy). 

Classwagon

While not the most practical vessel in the traditional sense, the Classwagon certainly has benefits to offer.

As a spaciously walled-in vehicle, it is fully furnished with bedding for six Medium-sized creatures and reinforced planarglass that can guarantee a safe night’s rest in any location. Used in combat, however, this vessel hinders its passengers and pilot with disadvantage on all attack rolls, with the exception of any attacks made by Eldritch Cannons.

While piloting the Classwagon, your driving speed is always 25 feet. It is Very Large in size, with 6 seats and a maximum of 200 hit points.

Ghost Pearl

The Ghost Pearl is an impressively quick vessel with a driving speed that is always 60 feet. While driving it, you gain advantage on DEX saving throws and all attacks against you are made with disadvantage, so long as the vessel moved at least 20 feet on your last turn.

The Ghost Pearl is Medium in size. It has 1 seat and a maximum of 45 hit points. 

Tornado Cage

The Tornado Cage is a dynamic vessel, equally advantageous in and out of combat. While driving it, your movement is always 40 feet. You also gain advantage on CON saving throws and resistance to slashing damage while in the vessel.

The Tornado Cage is Large in size. It has 2 seats and a maximum of 80 hit points.

Eldritch Innovation

Starting at the 5th level, you may choose one Eldritch Cannon from the Artillerist subclass to be permanently affixed to your Mystic Vessel.

Your Eldritch Cannon requires an action to activate (instead of a bonus action). It has an AC 18 and 50 hit points. When you repair your vessel, you may attribute any amount of restored hit points to the Eldritch Cannon instead.

Once the vessel is destroyed, your Eldritch Cannon will cease to function until the vessel is repaired. It is not removable and it does not occupy any space mechanically or cause the vessel to occupy any more space than it otherwise would. 

Flamethrower

The cannon exhales fire in an adjacent 15-foot cone that you designate. Each creature in that area must make a Dexterity saving throw against your spell save DC, taking 2d8 fire damage on a failed save or half as much damage on a successful one. The fire ignites any flammable objects in the area that aren’t being worn or carried.

Force Ballista

Make a ranged spell attack, originating from the cannon, at one creature or object within 120 feet of it. On a hit, the target takes [roll]2d8[/roll] force damage, and if the target is a creature, it is pushed up to 5 feet away from the cannon.

Protector

The cannon emits a burst of positive energy that grants itself and each creature of your choice within 10 feet of it a number of temporary hit points equal to 1d8 + your Intelligence modifier (minimum of +1).

Infusion Chamber

Starting at the 9th level, your Mystic Vessel is equipped with an Infusion Chamber. Once per long rest, you may use the Special Infusion action to infuse an item with two Artificer Infusions, rather than one.

The Special Infusion takes 2 hours to complete. Any other items with active infusion effects bestowed by you instantly turn to dust upon completion. The Special Infusion cannot be done if you have already performed an Infusion since your last long rest, and precludes you from performing any other Infusions until your next long rest.

Mystic Modules

Starting at the 15th level, your dedication to the art of Astroficy inspires you, granting you access to modules that may be installed on your Mystic Vessel and exchanged once after each long rest.

The list below includes mere examples of what you can do with modules. At any time, you may come up with another idea for a module and install it after your next long rest with your DM’s approval.

• Windy Module

In addition to your normal movement options, your vessel gains the ability to fly. Your flying speed while piloting the vessel is always half your driving speed.

• Washed Module
  

In addition to your regular movement options, your vessel gains the ability to swim and dive. Your swimming and diving speed while piloting the vessel is always half your driving speed.

• Harsh Module

Whenever you would roll for damage caused by your Mystic Vessel or any Eldritch Cannon affixed to it, add one additional die to your damage roll.

• Delicate Module

Whenever you would roll for damage caused by your Mystic Vessel or any Eldritch Cannon affixed to it, you may roll twice as many damage dice at the cost of half of your Mystic Vessel’s maximum hit points.

• Bright Module

Your vessel now emits a vibrant light in a 120-foot circle around itself, which can be magically switched on or off by the pilot at will. Any creature within 20 feet of the vessel when the lights are switched on must make a CON saving throw with a DC 14. If it fails, it suffers from the blindness condition for the next 5 minutes.

• Silent Module

Your vessel gains a magical sound barrier. Any actions taken from within the vessel are considered stealthy, unless expressly stated otherwise, and all stealth checks from within the vehicle are made with advantage.