Gearhead

The Gearhead is a character with a knack for everything mechanical and a love of explosions; They are capable of understanding, disabling and recreating locks, traps, and other things of a mechanical nature. In addition a Gearhead may use their mechanical and alchemical knowledge to create firearms and bombs, given adequate components and workspace. With access to the appropriate knowledge and materials, a Gearhead is capable of creating Arcane weaponry and even Constructs. Their primary attributes are Intelligence and Dexterity.

Gunsmith

character can use tinker's tools to craft ammunition, repair damaged firearms or craft and create new ones (DM discretion), gain proficiency in firearms combat.

If a critical fail occurs while attacking with a firearm the Gearhead must roll a percentage; 15% or less results in an explosion which does 2d6 points of fire damage and destroys the firearm; above 15% results in the firearm jamming. The Gearhead must then spend the rest of their turn making a repair roll (DC18) with their tools in order to use the weapon next turn.

The destruction DC is lowered to 10% at 7th level and 5% at 13th level.

Arcane Gadgetry

Using the appropriate material components and a gem or crystal worth at least 50gp, the Gearhead can imbue any single spell included in their design book into machinery, weaponry, or other gadgetry. Time and components required will depend on the desired result.

Since Gearheads do not have spell slots the process of imbuing a spell is treated like a ritual casting. The base amount of time required to imbue a spell is 10 minutes; add 10 minutes for every level of the spell above a cantrip. ex; Darkvision is a 2nd level spell and thus requires 30 minutes of uninterrupted casting time. True Seeing is a 6th level spell, so it would require 70 minutes of uninterrupted casting time). 

A Constitution save vs. Exhaustion must be made for each casting: 

DC 10 for Cantrips and 1st level spells; 

DC15 for 2nd and 3rd level spells; 

DC20 for 4th and 5th level spells; 

DC25 for 6th and 7th level spells; 

DC30 for 8th and 9th level spells.

For spells of a higher level than a cantrip roll 1d4 + Intelligence Modifier then divide by the level of the spell (rounded down) to determine the number of uses per day (1d6 at level 8, 1d8 at level 13); for a minimum of 1 and a maximum of 4.

Scientific Method

Gain proficiency in the Arcana skill, Alchemist's Supplies, and Tinker's Tools; a Gearhead is able to take Expertise with them as well. If the Gearhead Rogue beats a Lock or Trap DC by 5 points or more they will be able to recreate that mechanism perfectly for the next 30 days, as if with the Keen Mind feat. If the rogue draws the blueprints in their design book they will be able to retain it indefinitely (or until the design book is lost or destroyed).

Mad Genius

Gain advantage on all rolls against locks, traps, and machinery. If the subject of the roll is of a design included in your Design Book the DC difficulty is lowered by 10

The Spark of Creation

Gains the ability to create mechanical constructs using Tinker's Tools. The Gearhead must have appropriate components for each construct including mechanical components and gems or crystals of a high enough quality to act as power source and programming storage. Using the spell Command, the Gearhead is able to create constructs which can serve a variety of simple purposes. (The Gearhead must have the spell Command copied into their design book)

With appropriate tools and equipment the Gearhead can create their own mechanical components; gears, switches, casing panels, etc, just as when crafting firearms. The form of locomotion and other design elements are entirely up to the Gearhead (and DM discretion).

For the creation of a construct the gem or crystal must be worth at least 300gp per construct.

Automaton Savant

Gains advantage on ability and attack rolls against hostile mechanical constructs and automatons

Design Book

the journal or notebook in which the Gearhead records all of their favorite blueprints and experiments; blueprints for traps, locks, gadgetry, or constructs; firearm projects; or spells for the purpose of imbuing into various machinery. All spells must be from the Wizard spell list; what spells they are capable of transcribing coincides with Wizard spell progression. The Design Book also serves as a quick reference for tinkering and lab notes; enabling the Gearhead to recreate traps, or research things they have encountered in their adventures. Keeping a thorough record of such items drastically increases the Gearhead's ability to do what they do best; stealthily work their mechanical magic.