The Mechanist Forgemaster

Your patron is from the orderly plane of mechanus or one like it. Perhaps it's even the Primus himself. Whoever it is, you have been imbued with power over machines and the ability to create order from chaos.

If you've ever wanted a warlock subclass which was somewhere between a clockwork soul sorcerer and an artificer, this subclass is for you. Charisma and intelligence will both be important for this subclass, so don't dump intelligence.

Expanded Spell List

The Mechanist Forgemaster lets you choose from an expanded list of spells when you learn a warlock spell. The following spells are added to the warlock spell list for you.

Mechanist Forgemaster Expanded Spells

Spell Level	Spells
1st	grease, identify
2nd	heat metal, arcane lock
3rd	tiny servant, protection from energy
4th	fabricate, summon construct
5th	animate objects, creation

Bonus Cantrips

At 1st level, you learn the shocking grasp and mending cantrips. They count as warlock cantrips for you, but they don’t count against your number of cantrips known.

Maintain Order

1st level Mechanist Foremaster feature

A number of times per short rest equal to your intelligence modifer (minimum 1) you can treat a d20 you rolled as if it had rolled an 8 (modifiers still apply). You can do this instead of rolling or after you roll, but you may not do this to a roll in which you rolled a 1.

Mechanized Pact

Select the modified pact that corresponds to the pact boon you choose for your character at level 3. The options are listed below, but will not be selectable until level 3.

Pact of the Chain: your familiar is a construct instead of a celestial, fey, or fiend. The spell costs 10 gp worth of metal scraps and gears instead of 10 gp worth of charcoal, incense, and herbs.

Pact of the Tome or Talisman: your tome or talisman can be magically commanded to take the form of a set of artisan's tools or to revert from that form. You pick which set when you gain this feature, you gain proficiency with that set of artisan tools.

Pact of the Blade: if you take improved pact of the blade, the weapon you summon can be a firearm if your DM allows firearms.

Pact of the Mechanized Blade

Your pact weapon from Pact of the Blade (if you have taken the improved pact of the blade invocation) can be a firearm if you are playing with firearms.

Pact of the Mechanized Chain

Your Pact of the Chain familiar is a construct instead of a celestial, fey, or fiend. The spell costs 10 gp worth of metal scraps and gears instead of 10 gp worth of charcoal, incense, and herbs.

Pact of the Mechanized Tome or Talisman

Your Book of Shadows from Pact of the Tome or amulet from Pact of the Talisman, can be magically commanded to take the form of a set of artisan's tools or to revert from that form. You pick which set when you gain this feature, you gain proficiency with that set of artisan tools.

Eldritch Cybernetics

6th level Mechanist Forgemaster feature

You are considered a construct in addition to being a humanoid. 

You do not need to eat, drink, or breathe.

You have advantage on saves against being charmed and poisoned.

You have resistance against necrotic and psychic damage.

While you are not wearing any armor, your Armor Class equals 10 + your Dexterity modifier + your intelligence modifier. You can use a shield and still gain this benefit.

Reassembly

10th level Mechanist Forgemaster feature

The mending cantrip gets a casting time of 1 bonus action for you. Whenever you cast it on a construct (including yourself), that creature may expend of its hit dice to regain hitpoints equal to the hit die roll plus your intelligence modifier. If the creature doesn't have hit dice, it only regains your intellgence modifier in hit points.

Boon of the Forgemaster

14th level Mechanist Foremaster feature

Your patron has seen fit to bless you with the knowledge and materials to construct a personal guardian.

You gain a Master's Amulet and the according shield guardian as a companion with the following adjustments. The Shield Guardian's AC equals 12 plus your intelligence modifier and its hp equals your Warlock level times your intelligence modifier. It possesses a number of hit dice (d10s) equal to your Warlock level.

If the amulet or guardian are destroyed, you can implore your patron for another one. Your patron will grant your request at the end of your next long rest. However, your patron will require you to provide 300 gp worth of metal and gears to build a new shield guardian (your patron requires no payment for a new amulet).