Dwarven Steam Weaponry

As the great stronghold of Wawmar was nearing completion, the dwarves turned their attention to the design and fabrication of weapons. They had a few parameters in their favor. First, the nature of dwarves was such that they are willing to work hard to build such machinery, and they find a fascination with simple machines (levers, screws, wedges, etc.) and their applications to more complicated gadgetry. Second, the abundance of metals of high tensile and compressive strengths and good workability (steel, iron, copper, brass) made it possible to leap from the usual wooden construction to more durable, dependable equipment. Third, the dwarves had great understanding of the physical world and of static and dynamic systems.

For the most part, these weapons were designed, prototypes built, and plans were sold to gnomish tacticians who, with help from Wawmar's industrial prowess, were able to build and operate them. Wawmar's defenders and military minds saw little use or need for such weaponry, as the stronghold was generally considered to be impregnable. Of course this was before the rise of Stor-gris.

Several types of siege weapons were already in use in the known world, starting with the standard bows and atlatls, onagers, trebuchets and crossbows. But the dwarven interest in steam and their very fertile imaginations led them to a study and eventual merging of the two into very powerful, highly accurate and repeatable weapons.

Steam Driven Ballista

This powerful crossbow has a steam powered engine which automatically re-cocks the crossbow after a missile is fired.

The dwarves had already designed and built quite a few ballistas, but such weapons took on a different look with the introduction of steam power. The standard ballistae were built so that the power for launching was provided by twisted rope, which was a highly tenuous method. The skeins were short-lived, due to the tremendous strain applied and the fact that the strands were constantly rubbing on one another. And the mechanics of them were limited, as the bow only applied force to the projectile until the string was taught. The dwarves devised a different mechanism whereby the arms would travel inwardly, on an arc past each other, then push forward until the string was taut on the front end of the machine, almost doubling the amount of distance the force had to accelerate the projectile. This weapon was capable of increasing the velocity of the standard large bolt from the accepted norm of 400 feet per second to well over 700, which also made the arrow hard to track by sight and hard to avert.

The method, as stated, of transfer of power had to be changed, however, as the wrapped skein of rope could only be counted on for about 90 degrees of arm swing before the rope became loose and ineffective, as compared to the reflex type of the mechanism, which needed almost 180 degrees of travel. For this, the dwarves applied a rack-and-pinion type of motivation, whereby the rack would spin the spindles, which would in turn move the arms (see drawing, firing sequence). To reload a standard ballista, it was necessary to pull back the arms against a twisted-rope-force, where in this instance, it was merely necessary to pull back the rack against little force.

Steam Driven Ballista

Large object
Armor Class: 15
Hit Points: 75
Damage Immunities: poison, psychic

It takes a bonus action to load this massive crossbow, an action to aim it, and an action to fire it.
   Bolt. Ranged weapon attack. +6 to hit, range 120/480 ft., one target. Hit: 16 (3d10) piercing damage.

Flying Crossbow

This rare steam-driven weapon harnessed the power of steam to move several wheels/gears and pulleys. The advantages of this machine was the wide range of ammunition it could fire as well as how rapidly it could fire. Typically, one sharpened log was used as ammunition, although it was specialized ammunition known as "Many Shot" that made this weapon devastating on the field of battle. Five crew members are required to man the flying crossbow, and it takes 5 minutes for the steam engines to warm up before use. However, once activated and manned by a full crew, the Flying Crossbow will fire at a quick rate. The steam engine functions for 5 minutes on a 4 gallons of water.

Another weapon invented by the dwarves was the steam-powered flying bow. It was not really a bow, but a trough, or ramp, lined with wooden wheels. The wheels were arranged in pairs, each tilted inward, with successive pairs lining the length of the ramp. They were motivated by wooden-cog gears on the bottom, thereby synchronizing them from one side to the other. The power was supplied by a steam vane turbine through an endless rope loop, which contacted the spiked rims of the bottom cog gears, synchronizing each set of two wheels with the next. During operation, the matched set of 12 to 20 wheels spun in unison. Along the outer rim of the wheels were spikes pointed radially outward. To fire, the weapon was brought up to speed and a projectile was simply dropped on the rear wheels. The spikes grabbed the bolt and "passed" it on to the next pair, accelerating the shot forward to the end. The beauty of this weapon was its repeatability. Once the first bolt had been fired, the wheels would take 2 or 3 seconds to reach speed, and another bolt could be dropped. Needless to say, this was not a very transportable machine, and was used in defensive postures only. Due to the highly complicated nature, only two were ever made, as rope, gears, spikes and bearings were high-maintenance items. But when operating properly, it was a feared death-dealer.

To power these weapons, a dependable source of steam had to be designed, tested and built. The design consisted of two tanks, made from hammered and riveted copper. The upper tank served as a pre-heater, using exhaust from the fire that heated the lower, steam tank. Water was introduced into the upper tank, and when the steam was used for a firing, the water was released to the lower one, where the pressure was built to working limits.

The pressure was monitored by an ingenious method of "pinging", whereby the operator tapped the tank at the same precise location, listening to the sound. When the proper pitch was attained, he knew that sufficient pressure was available. Usually, most operations involved several tank systems for each of the heavier weapons, depending upon the amount, purity and pressure of the fuel gas. The dependability and working life of the generator, and of the weapons themselves, varied greatly, as many parameters were involved and many could, and did, go wrong. Several times, the equipment had to be shut down and carted away as piping or riveted seams burst, sometimes causing injuries to the operators. The chosen projectile for most of the mass guided weapons was the manyshot. This was a simple but deadly tool. A 2 to 4-inch diameter tree was cut to length and trimmed of bark. A sharp axe was run down the length of the trunk, cutting the fibers most of the way through, leaving a few in place to hold the individual arrows together. The front end of the bundle was dipped in molten lead and quickly quenched. The rear of the bundle was roughed up with a sharp hatchet to provide "feathers" to the arrows. When fired, the manyshot would break up and split into several arrows, and depending upon the pressure, velocity, and shape of the tube, would spread into an adjustable pattern to strike multiple targets.

Flying Crossbow

Large object
Armor Class: 13
Hit Points: 60
Damage Immunities: poison, psychic

It takes a free action to load this massive crossbow, an action to aim it, and an action to fire it.
   Bolt. Ranged weapon attack. +6 to hit, range 100/450 ft., one target. Hit: 10 (2d10) piercing damage.

Many Shot

Flying Crossbows also may use many shot, an alternate ammunition, which is in essence several smaller bolts tied together. Anywhere between 7 and 19 of these bolts could be assembled, causing a devastating (if erratic) barrage at the enemies. The range of many shot is significantly less than normal, only 1/4 of the typical range. Treat a many shot bolt fired from a flying crossbow as a separate attacks (between 7 and 19), but each attack is made with disadvantage. Cost per unit of ammunition ranges between 35 sp to 95 sp, based on the number of bolts per shot.


The large catapult has a steam powered engine which aids in the reloading and aiming of the device. It takes five crew members to load and prepare this device.

The steam powered catapult was then invented. It was a direct descendent of the standard catapult that was used by others for centuries, but with a very important difference. Other such weapons were driven, or fired, by using twisted skeins of rope. The rope was twisted by turning geared lugs along the sides of the frame, with the throwing arm thrust in between the plies of rope. As the arm was pulled back with winches and capstans, the rope twisted, providing a tremendous source of stored power. But this method of loading required time and a lot of mechanical movement, resulting in a long cycle time. Therefore, several catapults were required to be effective. Further, its rope system was suseptible to breaking and wearing of the rope.

The dwarves solved this by using steam. One end of a long rope was attached to a steam cylinder, the other to the arm, which, when activated, pulled the arm forward. As the steam cylinder could only produce limited speed, the rope was attached very close to the axle, providing very high mechanical advantage. For each inch of travel of the rope, a foot of travel could be expected for the projectile, thereby multiplying the speed of the cylinder twelvefold. The size of the piston, when multiplied by a meager 100 PSI of steam, would give tremendous force to the load. The steam generator was usually installed on the frame of the machine, which was mounted on wheels to allow quick retrieval of the weapon in the case of unexpected retreat. The steam powered catapult had its drawbacks. Many soldiers feared using it, as it was tricky to operate, and required constant monitoring and maintenance.

Steam Catapult

Large object
Armor Class: 16
Hit Points: 75
Damage Immunities: poison, psychic

It takes an action to load this weapon, two actions to aim it, and an action to fire it.
   Catapult Stone. Ranged weapon attack. +4 to hit, range 200/800 ft. (can't hit targets within 60 ft. of it), one target. Hit: 27 (5d10) bludgeoning damage.

Monager (Light Catapult)

The small catapult has a steam powered engine which aids in the reloading and aiming of the device. Two crew members can load and prepare this device.

The dwarves next invented the steam-powered monager. It was fired using twisted skeins of rope, as with earlier catapults, but the reloading of the weapon was aided by steam, instead of steam providing the driving force. A rack and pinion system built into each side of the machine, along and parallel to the bottom members, turned the pinions that twisted the rope skeins, tightening them to provide driving force. The steam pistons could be driven back, allowing the arm to fall to the rear and be reloaded. The racks were then driven forward, applying torsion, and the monager was fired. Cycle time then depended not upon how many soldiers could pole the gears at a time, nor upon how many could tug on a single set of ropes, but how fast the steam would drive the pistons. The monager was preferred by many armies over the steam catapult, although its range was not as great nor its final projectile weight as great. The interesting name was derived from the fact that it would kick like a wild ass, or "monager," each time it was fired. This was because its cylinders were mounted low, on the front of the machine, providing little resistance to the overturning effects of the residual torsion, making it "kick."


Large object
Armor Class: 14
Hit Points: 65
Damage Immunities: poison, psychic

It takes a bonus action to load this weapon, two actions to aim it, and an action to fire it.
   Monager Stone. Ranged weapon attack. +4 to hit, range 180/720 ft. (can't hit targets within 40 ft. of it), one target. Hit: 16 (3d10) bludgeoning damage.

Monager and Catapult Shot

Also known as grapeshot, this alternate ammunition was made of several small, hard items, designed to hit a large radius of creatures (20' radius). Super-heated sand, small pebbles, and even silverware have been used for shot. Cost per unit is based on what is used - typically whatever may be available at the time. Damage is piercing and bludgeoning, affecting all in a 20' radius, but the attack is made with disadvantage.


The most powerful of the steam-powered siege weapons, the trebuchet has a steam-powered engine which aids in the reloading and aiming of the device. Six crew members can load and prepare this device.

The most majestic of all siege weapons, the Trebuchet, was a feared machine. Its most important parameter was its range, and naturally, the use of steam was a very interesting possibility. The limiting factor, however, was the range of motion and movement of the hurling arm, as it had to swing through an arc unimpeded, just to release its left-over motion and energy. This precluded the use of steam, in the design stage, for quite a few years. The dwarves solved this problem in a simple manner. They figured out that installing a steam piston at any angle but directly in line with the swing of the arm would impose unwanted side stresses to the framework. And installing it in line would subject it to the fury of the short end of the arm as it completed its travel. Further, if the short end of the arm didn't have a counterweight, the arm would be almost uncontrollable once the payload had been shot. This problem was solved with sheer mass. The dwarves beefed up the axle and pinions of the hurling arm, building them by joining the framing sides in a triangle, allowing the heavy side logs to support the axle, rather than using a separate pinion. The front logs were extended and used, along with a sling, to "catch" the arm after it released the projectile. The steam cylinder was then installed as close to in-line as possible, but just far enough to the side to allow proper operation. Through numerous prototypes and tests, they ascertained the minimum construction parameters.

The performance of the mighty wooden monster was impressive. A modest charge of 100 pounds per square inch of steam, over the breadth of a 12" piston, was sufficient to accurately hurl a 150 pound stone a distance of up to 800 feet. This allowed the trebuchet to be operated out of the range of accurate arrow volleys. Its mass also allowed gnomes to hide from the arrows, as few could navigate through the mass of heavy logs positioned in various directions. The most effective weapon to use against a wooden trebuchet, that of fire, was still a possibility. A few flaming arrows could be launched from a castle, and a gnomish artillery company had to guard against this. The log sides were often fitted with ladders to allow buckets of water to be carried to put out flames. The dwarves realized that a machine of this size was too cumbersome to haul around, so they wrote and drew up a detailed specification for the sizes of the members, so that the weapon could be fabricated from logs and a few other items, normally found in the woods and forests found around most castles of the day. Most of it had to be built laid down, then assembled under cover of darkness or, in some cases, a darkness spell.

Steam Trebuchet

Huge object
Armor Class: 15
Hit Points: 130
Damage Immunities: poison, psychic

It takes an action to load this weapon, two actions to aim it, and an action to fire it.
   Trebuchet Stone. Ranged weapon attack. +4 to hit, range 300/1200 ft. (can't hit targets within 60 ft. of it), one target. Hit: 39 (7d10) bludgeoning damage.

Alchemist Cannon

Also known as a scorpion, this is a long, open ended tube shaped object, approximately 5 feet long. A trigger mechanism activates the steam engine, which hurls alchemists fire in a spray. Reloading an Alchemist Cannon requires 5 flasks of alchemist fire (as well as 1 gallon of water for the steam engine).

The third steam-fired weapon was the Alchemist Cannon. It bore a resemblance to a shoulder-fired cannon, much like the steam-powered crossbow, but was, in fact, lighter. The barrel of the cannon had to be made of thin, hammered and riveted copper sheets, as the heat from the alchemist fire was too damaging to a wooden barrel. The weapon was powered by an integral steam generator, but some models were charged by a separate steam generator, dragged along on wheels or on horseback. It consisted of a brass tank, fed by a tank of compressed gasses. A quart of water was usually good for quite a few shots, at which point it required refilling. It had a very advanced loading feature, in that the alchemist fire could be poured into the breech through a closeable nipple and funnel. The cost of this weapon was centered mostly around the manufacture of the barrel, since hammered sheets were produced by intensive methods and much labor.

Alchemist Cannon

Medium object
Armor Class: 12
Hit Points: 20
Damage Immunities: poison, psychic, fire

It takes 5 actions to load this weapon, whereupon it can be fired five times without loading it, a free action to aim it, and an action to fire it.
   Alchemist fire. Ranged weapon attack. +4 to hit, range 30 ft./60 ft., one target. Hit: 2 (1d4) fire damage at the start of each turn. A creature can use an action to make a DC 10 Dexterity saving throw to end the damage by extinguishing the fire.

Bessy Mauler

Only the strongest of creatures can wield this weapon, which is in essence a large-sized heavy crossbow. A Bessy Mauler is a martial ranged weapon.

The second steam-fired weapon was the Bessy Mauler. It bore a resemblance to a normal crossbow and was capable of being carried by a single soldier. The soldier had to be very strong, as the Mauler was a heavy weapon with equally heavy recoil. It differed fom other steam-powered "crossbows," as it was breech-loaded. The hollow tube, built as in above, was equipped with a trap door at the rear. This door was actually part of the tube, carefully cut with a fine saw so as to maintain good fit and to minimize leakage. The trap door was opened and a bolt was inserted. As the trap door closed, it meshed with the surrounding tube and locked into place. This was important, as the door was situated near the operator's face. Sighting along the tube, it was fired at will (when steam pressure was sufficient), and could be fired in a prone or tripod position, which added to its stealthy nature. The heavy recoil would put great strain on the shoulder of the operator, so the tripod was the preferred method. The weight of the weapon was mostly due to the integral steam generator. It consisted of a brass tank mounted below the barrel, fed by a backpack tank of compressed methane (or, in some cases, other flammable gasses). A quart of water was usually good for quite a few shots, but would require refilling. The breech-loading nature allowed reloading in the prone or in a safer position.

Bessy Mauler

Cost: 100
Damage: 2d8 piercing
Weight: 30 pounds
Properties: ammunition (range 120/420), heavy, loading, special, two-handed

A user makes attack rolls with disadvantage, as the weapon has a powerful recoil. The user may compensate for this and avoid the disadvantage by either using a tripod or by lying prone when firing. After every 10 shots, 1 quart of water must be added to the steam engine. Refilling the steam engine takes two actions.


This portable, three-legged device is used in conjunction with the Bessy Mauler. When the Bessy Mauler is mounted on the tripod, it absorbs the recoil, allowing the user to fire a Bessy Mauler without disadvantage. Assembling or moving a tripod takes an action. The tripod weighs 10 pounds and costs 50 sps.