A portmanteau of artificer and fixer, a classically dubious title with illicit connotations.

An Artifixer is a Rogue with a talent for killing and a knack for smithing. They hone their craft through borrowed knowledge of Artificers and applied use through weaponry. They are assassins with a laser focus on equipment, to elevate their craft to new heights. Through their understanding of baseline artificery they employ limited magic that they channel and wield physically. They are well versed in the mechanical applications of weapons and how to leverage them with utmost precision and use them as a means to line their pockets and chase their passions. 

Repertoire

At third level when you take this subclass your thieves tools become expanded as your expertise spreads. You incorporate Smithing Tools into your Thieves Tools and gain the ability to use your Thieves Tools in place of Smithing Tools for any check that requires them. You also gain the Mending Cantrip that use your Thieves Tools to cast to calibrate and maintain your weapons.

Calibration

Also at third level you gain the insight to take the knowledge you've gained from artificer smiths and apply a limited capacity yourself. Whenever you finish a long rest you can recalibrate a weapon to better fit your needs. This allows you to apply the Finesse property to a weapon that doesn't already have it as well as convert its damage type into another among slashing, piercing, or bludgeoning. You are proficient with any recalibrated weapon and can maintain a number of recalibrated weapons equal to half of your proficiency bonus rounded up.

Ex(tra)calibur

Finally at third level you gain another use for your bonus action. At the cost of your reaction you can make an additional weapon attack with a recalibrated weapon and add half your sneak attack die to the damage if it hits. You can apply the sneak attack damage to a number of attacks equal to half your dexterity modifier rounded down and regain all uses after a short or long rest. Sneak attack conditions must still be met.

High Calibur

At ninth level your ability with recalibrated weapons expands. As you hone the craft, the limited magical works borrowed become second nature allowing you to wield them far more effectively than an ordinary weapon. When you take the optional bonus action attack you can apply the full amount of sneak attack die as long as you hit with the attack action that same turn. 

Overloaded

At thirteenth level you weave your Mending cantrip into the calibrarions to strengthen your attacks. Whenever you or an ally within 5 feet of you take damage, you can choose to have a portion absorbed automatically into your weapon(the target still takes the full amount) and becomes charged. This adds an extra d6 to the first sneak attack that lands afterwards for every 10 points of damage taken. This feature can be used once and regains it's use after a long rest.

True Calibur

At seventeenth level your mastery over the tools of your bloody trade have hit their peak. Whenever you apply your sneak attack damage on the bonus attack, the damage die increases from d6's to d8's.