Here’s a class I liberally adapted for Castles and Crusades from Dragonmech (d20). I hope someone finds it useful, or at least interesting.
A steamtinker is fantasy inventor that fuses magic, steam engines, and clockwork in order to create amazing contraptions and weapons. The machines created by a steamtinker in many ways defy the laws of logic or physics. Even so, most steamtinkers refuse to think of their inventions as magical, preferring to consider them masterpieces of engineering. In any event, the devices are not affected by dispel magic. Most steamtinkers are dwarves or gnomes. Due to the intense training and discipline required of a steamtinker, most are lawful, although some “mad scientists” are very chaotic indeed.
STEAM POWERS (Intelligence): A steamtinker understands the techno-magic required to build amazing devices powered by steam. A steamtinker can build any number of such items given time and materials, but can only maintain a small number daily, equal to the character’s level + Intelligence modifier +1. To build or maintain a steam power, a steamtinker must have a proper tool kit (5 gp, 5 lbs.), and 1 lb. of coal for each device maintained (5 cp per lb.).
Daily maintenance requires 15 minutes for each device maintained, as well as an Intelligence check versus a CL equal to the number of devices maintained. If this check fails, a number of devices equal to the margin of failure do not function. The particular devices are chosen randomly, and the steamtinker does not discover that the devices will fail until an attempt is made to activate them under field conditions. A steamtinker can attempt to repair a device through emergency maintenance with an Intelligence check versus a CL varying with the expediency of the repair (CL 10 for 1 round, CL 5 for 1 minute, CL 0 for 15 minutes). If this check fails, the steamtinker must wait for the next day to maintain the item normally. Devices not properly maintained for seven consecutive days are effectively scrapped, but may be rebuilt at half cost.
STEAM-POWERED ARMOR AND WEAPONS: While a steamtinker has little familiarity with traditional armor or weapons, his or her deep understanding of steam devices allows the use steam-powered versions of such items without penalty. Any armor or weapon can be steam-powered. The item’s cost is quadrupled and its weight is doubled. Such devices require 8 man-hours to construct. Steam-powered weapons ignore their wielder’s Strength modifier to attack or damage rolls, adding their wielder’s Dexterity modifier to attack, whether in melee or ranged combat. Such devices must be maintained in the same manner as other steam powers, and count against the steamtinker’s devices per day.
PRIME ATTRIBUTE: Intelligence
HIT DICE: As Wizard
EPP PROGRESSION: As Wizard
BTH PROGRESSION: As Wizard
WEAPONS: Club, dagger, dart, staff, steam-powered weapons
ARMOR: Steam-powered armor
ABILITIES: Steam powers, steam-powered armor and weapons
SAMPLE STEAM DEVICES
Alarm Eye: Materials Cost: 120 gp, Weight: 1 lb., Construction Time: 8 man hours. Trains a faint beam of light on a stationary target within 50 ft. Any visible object that breaks this beam of light triggers an alarm claxon.
Air Tank: Materials Cost: 70 gp, Weight: 10 lbs., Construction Time: 8 man hours. Provides enough breathable air to sustain an adult human for one hour. If the tank bursts, a concussive blast of air knocks characters within 5 ft. prone unless they succeed on a Strength check (CL 2).
Brain Box: Materials Cost: 120 gp, Weight: 15 lbs., Construction Time: 8 man hours. Replaces the brain of a cadaver, enabling the corpse to perform crude actions, much like a zombie. The “steam zombie” is uncontrolled, and follows the same routine it did in life.
Buzzsaw: Materials Cost: 80 gp, Weight: 40 lbs., Construction Time: 8 man hours. Functions as a steam-powered variation of a two-handed axe (1d12 damage). A buzzsaw requires two hands to operate, and may be mounted on a hydraulic exoskeleton.
Chattersword: Materials Cost: 120 gp, Weight: 30 lbs., Construction Time: 8 man hours. Functions as a steam-powered variation of a two-handed sword (2d6 damage). A chattersword requires two hands to operate, and may be mounted on a hydraulic exoskeleton.
Dehumidifier: Materials Cost: 120 gp, Weight: 30 lbs., Construction Time: 8 man hours. Produces a pint of pure water each hour in normal climates, 2 pints in moist climates, 0.5 pints in dry climates.
Descrambler: Materials Cost: 320 gp, Weight: 1 lb., Construction Time: 8 man hours. Enables the steamtinker to pick mundane locks as a rogue of the same level. The process takes 1d20 minutes, and sometimes (5%) destroys the lock.
Drill: Materials Cost: 10 gp, Weight: 7 lbs., Construction Time: 8 man hours. Drills 6 inches per minute through solid stone, and can be used as a weapon causing 1d4 damage with a successful attack roll.
Gear Mail: Materials Cost: 200 gp, Weight: 60 lbs., Construction Time: 8 man hours. Functions as a steam-powered variation of scale mail (AC +4). Gear mail can be worn in conjunction with a hydraulic exoskeleton, although the latter provides no AC bonus in this case.
Hydraulic Exoskeleton: Cost: 400 gp, Weight: 50 lbs., Construction Time: 16 man hours. Provides AC +2 and serves as a stable chassis for additional devices such as hydraulic legs or fists. The exoskeleton doubles the encumbrance levels the character can lift and carry.
Hydraulic Fist: Cost: 400 gp, Weight: 50 lbs., Construction Time: 16 man hours. Functions as a battering ram, sledge hammer, or vice. The fist is too slow and awkward to be used in combat, but causes 3d6 damage to stationary objects.
Hydraulic Legs: Cost: 300 gp, Weight: 50 lbs., Construction Time: 16 man hours. Walks at a constant speed of 20 ft., carrying up to 1000 lbs. Once the legs are activated, they will continue to walk and require no attention from their wearer, allowing 24 hour travel over level ground.
Identifier: Materials Cost: 200 gp, Weight: 10 lbs., Contruction Time: 8 man hours. Breaks down materials placed within its centrifuge, revealing whether they are poisonous, and determining if they are magical or mundane in nature.
Light Generator: Materials Cost: 15 gp, Weight: 4 lbs., Construction Time: 8 man hours. Illuminates an area comparable to a torch with a glowing filament within a glass globe. The globe is very hot, causing 1d4 damage if touched, but is fragile and will break if impacted.
Mapper: Materials Cost: 50 gp, Weight: 2 lbs., Construction Time: 16 man hours. Incribes its movements to a desired scale onto an attached slate. The mapper must maintain constant contact with the floor in order to map an area accurately.
Prop Arm: Materials Cost: 1500 gp, Weight: 30 lbs., Construction Time: 16 man hours. Moves through the water at a swim speed of 20 feet per round (halved ascending, doubled diving). The prop causes 3d6 damage to any creature it strikes, but then spins out of control.
Rotor Arm: Materials Cost: 1500 gp, Weight: 30 lbs., Construction Time: 16 man hours. Lifts itself plus 350 lbs aloft at a flight speed of 50 feet per round (halved ascending, doubled diving). The rotor causes 3d6 damage to any creature it strikes, but then spins out of control.
Smoke Cloud Generator: Materials Cost: 250 gp, Weight: 5 lbs., Construction Time: 8 man hours. The smoke spreads in a 15 ft. radius, 10 ft. high, centered on the device. If operated continuously, the radius expands by an additional 5 ft. each round.
Steam Bow: Materials Cost: 200 gp, Weight: 18 lbs., Construction Time: 8 man hours. Functions as a steam-powered variation of a heavy crossbow (1d10 damage, range 120 ft.). A steam bow requires two hands to operate, and may be mounted on a hydraulic exoskeleton.
Steam Breather: Materials Cost: 300 gp, Weight: 25 lbs., Construction Time: 8 man hours. Belches forth scalding steam, causing 1d10 damage to all creatures in a 45 degree arch, up to a range of 10 ft. The 1 gallon water reservoir is exhausted after 10 rounds of operation.
Steam Cannon: Materials Cost: 3000 gp, Weight: 200 lbs., Construction Time: 24 man hours. Fires iron balls (6d6 damage, range 100 ft., 3 lbs., 3 sp) or shot (3d6 damage, range 30 ft., 3 lbs., 0 gp), every 30 rounds. Moving targets or targets smaller than a wagon are attacked at -4.
Steam Shovel: Materials Cost: 500 gp, Weight: 250 lbs., Construction Time: 24 man hours. Digs a hole 125 cubic feet (a 5 ft. cube) every minute of operation. The shovel is too slow and awkward to be used in combat, but causes 3d6 damage to stationary objects.
Voice Command: Materials Cost: 100 gp, Weight: 1 lb., Construction Time: 8 man hours. When affixed to another steam device, allows the device to be voice-activated and controlled at range. Remote operation is too clumsy for combat, but crude manual tasks are possible.
Voice Transmitter: Materials Cost: 65 gp, Weight: 1 lb., Construction Time: 16 man hours. Transmits and receives sounds through radio waves, much like a walkie-talkie. Effective range is 5-miles on a clear day with no obstructions. Underground use is limited to a few dozen yards.
Water Proofing: Materials Cost: 10 gp, Weight: -, Construction Time: 1 man hour. Enables a single steam device to function when wet. Most furnaces are easily extinguished (5% per round in rain, 25% per round in a deluge, 90% per round submerged). Water Proofing requires no coal.
"Adapted from material in DragonMech, copyright 2003 Goodman Games, all rights reserved. Used with permission."