In a world of magic, technology is pursued by a rare number of people. Gadgeteers are among those with an innate affinity for mechanical devices and technological innovation. These rogues love to tinker, invent and solve problems. They are masters of picking locks, disarming or setting traps, and finding clever solutions that others would not. Always resourceful, they tend to arm themselves with an array of tools, more so than weapons, and their clothes abound with pockets, straps, loops and pouches for carrying it all. 

Bonus Proficiencies

Starting at 3rd level, you gain proficiency in the use of all crossbows and proficiency in tinker's tools. Gadgeteers also gain Expertise with Thieves' Tools. If you already have this Expertise you may choose to have Expertise in one of either Investigation or Sleight of Hand. Additionally, you become a Jack of All Trades in regards to artisan's tools - you may add half your proficiency, rounded down, to any check using artisan's tools of any sort.

Minor Inventions

As a Gadgeteer you are always looking to innovate or improve on technology. You gain the ability to craft unique items using your tool proficiencies. The only drawback is that you must spend time and money. You have the same ability as a Rock Gnome to create Clockwork Toys, Fire Starters or Musical Boxes. Characters who are not Rock Gnomes, however, must spend 2 hours to construct one of these devices. 
Other items that Gadgeteers can craft at 3rd level are detailed below. It is not an exhaustive list and players and DMs are encouraged to be creative and collaborate on inventive devices that fit the technological level of the campaign world.

Special Use Arrows
You can create special arrowheads that can be fitted to arrows or crossbow bolts. They cost 5gp each to make and in one work day you can make as many as your proficiency bonus. Only Gadgeteers are considered proficient with the use of these specialty arrows. These arrows are good for a single use only. Firing these arrows halves the range of the weapon that fires them.
- Anchor arrows: Arrows that penetrate and hold firm in wood or stone, providing an anchor for an attached rope. The DM will determine the DC depending on the hardness of the material you are trying to penetrate. If used against creatures they do the normal damage of the weapon that fired them, though they will stick into constructs made of wood or stone.
- Bola arrows: These arrows hold three heavy balls connected by wire that deploy shortly after being fired. When aimed at the legs of a Small or Medium creature a successful hit means the target is effectively grappled. If the target was moving at the time, they must make a DEX saving throw or fall prone. Entangled creatures must spend one round to free themselves.
- Grapple arrows: These arrows have three strong hooks on the head. Much like anchor arrows, grapple arrows are useful for climbing, or for perhaps grabbing something from afar. 
- Whistling arrows: With tiny grooves in the arrowhead, these arrows create a loud, piercing whistle. This whistle can be heard from far away and can act as a signal. It may spook some animals. It is also very distracting and anyone within 50ft of its flight path cannot take reactions.

Improved Crossbows
The Gadgeteer can produce two different types of improved crossbows. Only Gadgeteers are considered proficient in the use of these weapons and they cannot combined with special use arrowheads. They cost double the amount of a normal crossbow and take a week to craft. 
- Double Shot Crossbow: This crossbow can fire two bolts one at a time, or in quick succession giving you an Extra Attack, even if you don't usually have one. However, it takes a full action to reload another double shot. It can be used as a normal single shot crossbow otherwise. It is 1lb heavier than a normal crossbow
- Repeating Crossbow: Using a lever, this crossbow is quickly and mechanically reloaded from a magazine of bolts (capacity of 10). It ignores the loading property and grants an Extra Attack per round. However, its effective range is diminished by half and its damage is reduced (1d4 for a hand crossbow, 1d6 for a light crossbow and 1d8 for a heavy crossbow). It is 3lbs heavier than a normal crossbow.

Simple Traps
Traps come in many forms, and below are just a few examples.  When creatures make checks to spot the trap, or saving throws to avoid the trap, use a DC of 8 + your Intelligence modifier + Your Proficiency Bonus
- Snares: Snares are simple traps that can be built with but a few materials. They are usually built in woody areas, where a bendable tree provides the spring action, and the trap can be easily camouflaged. Spending an hour of time, you can create a snare that will capture a creature of Tiny or Small size. With 2 hours of work, you can create a snare that will capture a creature of Medium size. Creatures caught in a snare take 1d4 points of damage and are  restrained.
- Needle Traps : These are small traps with small spring-loaded needles to deter people from opening or touching certain objects. Gadgeteers often have many of their own items trapped in such a way, for those unlucky enough to try and steal from them. The needle itself does 1hp of damage, but it is usually the delivery method for some kind of toxin. The DM will determine the availability of poison and the amount of poison damage. Needle traps cost 10gp to make and take 1d4+1 hours to build.
- Trip Wire or Pressure Traps: Larger traps that use a trigger to spring a deadly effect come in a variety of forms, from bear traps to scything blade traps. The DM will have to use their discretion in determining if materials are available and the cost of those materials.They may roll 5d20 to randomly determine cost in gp to build the trap, and 1d4 to determine how many days it takes to build. In general, these traps should be able to impose a condition (such as restrained) and/or do no more total damage than the Rogue's Sneak attack for their given level. The more creatures the trap is meant to effect, the less damage it will do per person.

Locks
Gadgeteers are proficient locksmiths. They can create locks just as easily as they can pick them. The difficulty of picking your locks is equal to a DC of 8 + your Intelligence modifier + your proficiency modifier. You can craft a key lock for 10gp and 1 day of work. Combination or puzzle locks cost 25gp and 1d4 days to craft..

Concealable weapons.
The following weapons cost 50gp and 5 days to craft. Only Gadgeteers are considered proficient in their use.
- Folding Bow: This is a shortbow that can be folded to half its length, making it much more concealable. You use a Bonus Action to unfold it and make it ready to fire.
- Spring-loaded blades: These are blades or spikes that can be concealed and drawn in an instant. They may attach to the wrists, be hidden in the soles of boots, on the end of a staff or in another hand held object. Using the element of surprise you gain Advantage the first time you attack in combat with a hidden blade, gaining the opportunity for Sneak Attack damage. Blades do 1d4 damage.
- Telescopic Baton. With a flick of the wrist, this club extends from a six-inch grip into a rigid two-foot long club. This weapon gives you Advantage the first time you attack in combat with it, giving you the opportunity for Sneak Attack Damage. It does 1d4 damage.

Other Inventions
Other devices a Gadgeteer might want to craft include mechanical clocks, listening devices such as stethoscopes or ear trumpets, measuring devices such as thermometers or barometers, compasses or astrolabes. The cost and time to craft these is at the discretion of the DM.

Alchemic Inventions

At 9th level you gain proficiency in alchemist's tools, if you don't already have it. With your creative skill and having unlocked the secrets of black powder, you are able to craft extremely rare and deadly weapons, which are detailed below.

Firearms
You are able to craft a flintlock pistol or musket. A pistol costs 200gp and 10 days to craft, and a musket costs 400gp and 20 days to craft. Each weapon fires one shot and requires a full Action to be reloaded. A Pistol deals 1d10 points of piercing damage and has a range of 100/400. A musket deals 1d12 points of piercing damage and has a range of 200/800. When attacking with a firearm, any die roll for maximum damage means that you can roll damage again. You can keep rolling if you roll maximum damage a second time, and so on. Only Gadgeteers (and Gunslingers if they are used in your campaign) are considered proficient with these weapons. When you make an attack roll with a pistol, a die roll of 1 (die roll of 2 or 1 for a musket) means that the weapon misfires. The weapon is rendered useless and takes one hour to be repaired with a successful tinker tool's check (DC 10). If the check fails then it requires half the weapon's cost to fully repair. These weapons require ammunition and a supply of black powder. Black powder and balls for 10 shots costs 50gp. Guns must be kept clean and dry, and need 20 minutes of maintenance on any day in which they were used. Otherwise the chance for misfire doubles. Anyone who is not proficient with these weapons and who regardless tries to use one, will trigger a misfire with any die roll of 5 or lower. They will also suffer fire damage equal to the weapon's damage. 

Incendiary Arrows
These are special function arrows that burst into flame when they strike. They have the normal range for the weapon that fires them. They deal an additional 1d4 points of fire damage and ignite combustibles. They cost 15gp each to make and you can craft two in a day.

Smoke Bombs
These small spherical missiles, made of clay and filled with an alchemical mixture, break upon impact and instantly produce a thick cloud of smoke that heavily obscures a 15ft area. A Gadgeteer can break one at his or her feet using their Reaction. The smoke thins and disperses after one round. They cost 15gp each and you can craft 3 in a day. Alternatively they can be crafted to fit onto an arrowhead or bolt, making them cost 20gp each, and you can make 2 in a day.

Wondrous Inventions

By 13th level, you have learned enough about the workings of technology that you can craft items of increasing complexity and uniqueness. Detailed below are three wondrous inventions. Again, players and DMs are encouraged to be creative in coming up with other possible non-magical yet wondrous devices that a Gadgeteer could create.  The following devices cost 500gp and take 2 weeks to craft.

Retractable Grappling Gun
This amazing hand crossbow launches a grappling or anchor bolt up to 60 feet. The bolt is attached to a light yet strong cord or wire that unspools from a powerful winch on the crossbow that recoils when triggered. Using your Action, the Gadgeteer can fire the gun and be quickly pulled to where the grapple has taken hold, moving the full 60 feet, while still having the rest of your movement available to you in the round. Using it to escape battle does not provoke attacks of opportunity. Conversely, it can be used to pull smaller things toward you. The recoil can be slowed or stopped as you wish. The line is strong enough to hold up to 400lbs of weight. Grapple bolts can be reused right away, but if an anchor bolt is used, it must be detached and a new one attached, which requires one action.

Helm of Seeing
This leather helmet is equipped with an array of lenses on movable mechanical arms that can be positioned in front of the wearer's eyes. Any of the lenses can be deployed as a reaction. It has magnifying lenses that allow the wearer to see very small things up close, or see things that are very far away. They grant Advantage on all Perception or Investigation checks relying on sight. Additionally it grants Advantage of any check relating to the use of tinker's tools. It also has lenses that help one see in the dark. These grant limited darkvision to a range of 20ft. If you already have darkvision, it extends it by 20ft. The helm also has darkened lenses that protect the wearer from being blinded by bright light granting Advantage to any applicable saving throw. It has a lens that grants Advantage on any saving throw to detect illusion. Lastly, it has a lens that can detect fluctuations in the Weave and as such grants the wearer the ability to detect magic. 

Glider Pack
This modified backpack contains extendable wings which can be deployed using your reaction. The wings allow you to glide if you launch or fall from a height of 30 feet or higher. You may glide up to 4 times as far as you fall and land safely at the end. You have a gliding speed of 60 and you can turn up to 45 degrees every 20 feet. You cannot take any actions while gliding that require the use of your arms. You may attack at the end of your flight, however, with Advantage.

Large Scale Inventions

When you reach 17th level, you are a master Engineer. You are considered proficient in every artisan's tools. You can design and oversee the construction of large scale projects, including siege engines such as trebuchets, catapults, ballista and even cannons. You can also design and oversee the construction of airships or submersibles. The cost and time to craft these devices is significant and up to the discretion of the DM.