The Mechanist

Mechanical Identity

The mechanist can fit a few roles in the party, all depending on the specialty the Mechanist chooses to be.
The Strider mechanists specialise in their ability to move around the battlefield, eventually obtaining the ability to attach gadgets to their Opus such as a grappling hook to get to high places, as well as a propulsion system which can give them temporary flight.
The Barracks is the big tank. They specialise in integrating weaponry into their Opus that allows them to have access to a full arsenal at all times. They get the ability to have integrated weaponry such as a pop out shield and wrist crossbows. They also wield the heaviest Opus.
The Catalyst specialise in integrating the various elements into their Opus. The are capable of throwing flames from their hands, or excavating the earth beneath them.
They can also form certain elements to form around
their opus to give them additional damage on hits.

Image Created by Dragonmech

Image Link - https://www.goodman-games.com/images/WW17604-7.jpg

Creating a Mechanist

When creating a mechanist, think about how your character managed to aquire the components needed to build such a complicated piece of engineering. Discuss with your DM how your character managed to come into the large sum of money to make your Opus. Are you part of a guild of tinkerers or blacksmiths? Are you from nobility so were able to easily fund your research? Have you accrued a large debt to someone so you can make your invention?
What led you to go on this adventure? To pay back what money you owe? Do you want to test your machine on the field? Are you on a dangerous mission for a someone your character knows? Also consider if being a mechanist is appropriate for your DMs campaign. Opuses are expensive machines. In world where coin and supplies are in short supply, it won't make sense.

Class Features

As a mechanist, you gain the following class features.

Constructing Opuses

Since only Mechanists are capable of constructing Opuses, you will be unable to get a new Opus at regular Blacksmiths. Potentially you could buy one off a fellow Mechanist, however the Opus would need to be refitted to allow you to fit in it correctly. This refitting costs 500gp for the new form fitting subframe and reshaping. This must be done over the course of 24 hours total of work with access to a forge and workshop.
To construct a new Opus requires you to obtain the costs worth in metals, leather, cloth and hydraulic liquids. Once you have obtained all the materials, you must have access to both a forge, workshop and alchemist supplies to actually construct the Opus. It requires a total of 72 hours of time spent constructing the Opus.
You can choose to upgrade your current Opus instead of constructing a new one. Doing so will allow you to subtract the cost of your current Opus from the total amount required to achieve the MK you wish to upgrade to (Example: If you have a MK1 Strider, instead of paying 2,500gp to construct a MK2 Strider, you can instead pay 1,000gp to upgrade your MK1 to the MK2).
The length of time required to upgrade an Opus is equivalent to half the time required to construct a new Opus (36 hours).

(Variant Rule) Opus Maintenance

Although a force to be reckoned with, an Opus is a high maintenance weapon. Regular check must be made to make sure it is in top condition. If left unchecked for too long, the Opus will start to underperform and seize up.
Maintenance must be performed every 15 days in which an Opus has been active (this allows you to not count days in which you are not wielding your Opus). To perform this maintenance, you require the use of Tinker’s Tools and Alchemist Supplies. You must spend 5gp of oil, metal and leather to perform this maintenance. Once maintenance has been performed, another maintenance check will not have to be done for the next 15 days.
On the 16th day where a check still hasn’t been made will mean you will start to accrue penalties until a check is made. For every 5 days over 15 day where a maintenance check still hasn’t been made, you will have a -1 to all Strength and Dexterity ability checks, attack rolls and Strength and Dexterity saving throws. This can stack up to a total of a -5 penalty at 40 days without maintenance.

Smart Fighting

Starting at Level 1, you can use your Intelligence modifier instead of Dexterity or Strength for the attack and damage rolls with all weapons. This is only usable while inside of an Opus.

Work Smarter Not Harder

Starting at Level 1, when making a Strength (Athletics) check or a Strength Saving Throw, you can use your Intelligence modifier instead of your Strength Modifier.

Opus Archetype

At level 1, you must choose what type of Opus you want to construct, a Strider, Catalyst or Barracks. They each have their own unique abilities and playstyles.
These features will only be usable whilst inside of an Opus. Your choice grants you new features at level 3, 6, 9, 11, 15 and 20.

Enchantment Integration

Starting at 2nd level, you can now integrate magical armor into your Opus, at the expense of the armor itself. Over the course of 3 long rests you spend on the integration of the item. You can attach the magical properties of magical armor, boots, helms or gloves to the Opus itself, allowing you to benefit from their abilities.
If you wish to integrate a piece of magical armor when you already have integrated an armor piece of that type into your Opus, you can still choose to integrate the new piece, at the expense of losing the magical ability of the previous piece.
You may have, boots, armor, gauntlet and helm enchantments all at once (Abiding by the attunement rulings).
You do not need to be proficient with the armour pieces to integrate them into the Opus. The integration process removes the required proficiencies.

Overclock

Starting at 2nd level, you can now make your Opus perform beyond what it is normally capable of. Once per encounter, you can Overclock which will allow you to perform 3 actions on one turn, however for the next 2 following turns, you cannot perform actions (bonus actions, movement and reactions are still usable for the 2 turns).
This ability recharges when finish a long rest.

Ability Score Improvement

When you reach 4th level, and again at 8th, 12th, 16th, and 19th level, you can increase one ability score of your choice by 2, or you can increase two ability scores of your choice by 1. As normal, you can't increase an ability score above 20 using this feature.

Extra Attack

Beginning at 5th level, you can attack twice, instead of once, whenever you take the Attack action on your turn.

Shock Absorbers

Starting at 7th level, you have perfected a method to absorb the damage normally received when falling from a great height. You do not take damage from falls up to 100 feet and half damage from falls greater than 100 feet. You also do not fall prone from falls up to 100 feet if you are the one willingly falling.

Protective Coating

Starting at 10th level, you have coated your Opus in a protective hydrophobic substance that will protect you from the nasty poisons and diseases found on adventures. While wearing your Opus, you are immune to poison damage and diseases, and are resistant to acid damage.

Shock Paddles

Starting at 10th level, while you are wearing an Opus and you are required to make a death saving throw on your turn, you can make a free medicine check once a turn to stabilise yourself before making the death saving throw.

Air Tanks

Starting at 13th level, you have fitted your Opus with air tanks and waterproofed it. You can now breathe underwater when wearing an Opus.

Reliable Overclocking

Starting at 14th level, you have worked out some kinks with your ability to Overclock. You no longer lose your next two turns actions when you use your Overclock ability. Additionally, you Overclock ability recharges when you finish a short or long rest.

Unstoppable Force Immovable Object

Starting at 17th level, you are now proficient with all Saving Throws and you now have advantage on all Athletics checks.

More Machine Than Man

Starting at 18th level, you have now started work on replacing organic material with your mechanist creations. You no longer need to eat or sleep, and you also no longer age. Additionally, you can now use your Smart Fighting and Overclock features when you are not wearing an Opus.

Ultimate Overclocking

You can now take your Opus to its utmost limits. You can now use your Overclock ability once per encounter.

Opus Archetypes

You may choose to specialise in one of three forms of Opus, the Strider, Catalyst or Barracks.

Uncanny Dodge

Starting at 6th, when an attacker that you can see hits you with an attack, you can use your reaction to halve the attack's damage against you.

Evasion

Starting at 9th level you have increased the speed in which your Opus allows you to dodge. When you are wearing a Strider Opus and are subjected to an effect that allows you to make a Dexterity saving throw to take only half damage, you instead take no damage if you succeed on the saving throw, and only half damage if you fail.

Overdrive

Starting at 11th Level, you are now unaffected by difficult terrain. Additionally, your movement speed is increased by 15 feet.

Propulsion System

At 15th level, you have fitted your Opus with an experimental propulsion system that will give you unmatched mobility on the field. You can now spend your bonus action to give yourself a 60ft Fly Speed that turn. Also on the turn this ability is activated, all attacks have disadvantage against you. This ability lasts a number of rounds equal to your Intelligence modifier.
You cannot use this ability again until after a short or long rest.

Renewable Cells

At 20th level, you can now use your propulsion system multiple times. You may activate the propulsion systems 3 rounds after the propulsion system has finished.

Catalyst

The Catalyst is for those who are the most daring (or psychotic). Adding dangerous doodads and untested and experimental weaponry to their Opus to harness the elements just as the arcane wielders can, but in a cooler way.

Acid Projector

The projector is a container strapped around the neck which will project acid from a valve near the mouth. You can cast the Acid Splash cantrip.
Slick Surface: You can 1 spend Charge to cast Grease.
(5th level required) Acid Spit: You can 2 spend Charge to cast Melf's Acid Arrow.
(9th level required) Fertilizer: You can 3 spend Charge to cast Plant Growth.
(13th level required) Acid Bomb: You can spend 4 Charge to cast Vitriolic Sphere.
(17th level required) Shock The Senses: You can spend 5 Charge to cast Contagion.

Poison Injectors

You have constructed sets of injectors into your Opus' bracers that hold potent poisons. You can cast the Poison Spray cantrip.
Stream of Death: You can 1 spend Charge to cast Ray of Sickness.
(5th level required) The Antidote: You can 2 spend Charge to cast Protection from Poison.
(9th level required) IT'S ALIVE: You can 3 spend Charge to cast Animate Dead.
(13th level required) Black Veins: You can spend 4 Charge to cast Blight.
(17th level required) Cloud of Death: You can spend 5 Charge to cast Cloudkill.

Voltaic Coils

You are now a walking power generator. You have arcs of lightning dangerously snaking across the metal plates of your Opus. You can cast the Shocking Grasp cantrip.
Arc Leap: You can 1 use Charge to cast Witchbolt.
(5th level required) Blue Dragon Imitation: You can 2 spend Charge to cast Dragon Breath but can only deal Lightning damage, and it has a casting range of 'self'.
(9th level required) Lightning Bolt: You can 3 spend Charge to cast Lightning Bolt.
(13th level required) Storm Sphere: You can spend 4 Charge to cast Storm Sphere.
(17th level required) Voltaic Fallout: You can spend 5 Charge to cast Destructive Wave. The damage you deal will be 5d6 thunder damage and 5d6 lightning damage.

Jackhammer

You have created pneumatic devices on each limb that are capable of sending forward concussive blasts. You can cast the Thunderclap cantrip.
Shockwave: You can spend 1 Charge to cast Thunderwave.
(5th level required) Concussive Blast: You can spend 2 charge to cast Charge to cast Gust of Wind.
(9th level required) Thunder Step: You can 3 spend Charge to cast Thunder Step.
(13th level required) Containment: You can spend 4 Charge to cast Otiluke's Resilient Sphere.
(17th level required) Bubble Shield: You can spend 5 Charge to cast Antilife Shell.

Additional Element

At 3rd level, you can choose an additional element. You can choose another element at 3rd, 9th and 15th level.

Weapon Infuse

Starting at 6th level, you have developed a method to infuse the elements you've attached to your Opus into the weaponry you carry as well. When in your Opus, you can now spend a bonus action and 2 Charge to infuse a weapon you have drawn with an element you have infused in your Opus. Your infused weapon will now deal an additional 1d6 in the damage you choose to infuse for the next minute.

Potent Mixture

Starting at 11th level, You can now add your Intelligence modifier to one damage roll of a Charge Ability. Additionally you can spend 2 extra charge when using a Charge based ability to ignore an enemy's resistance to the damage type. Enemies who are immune to the damage are unaffected.

Oppressive Atmosphere

Starting at 20th level, you have figured out how to tactically allow your instruments that hold your raw concoctions emit the substances straight into the air and seriously harm anyone other than yourself who is near to you.
As an action, you can spend 5 Charge to allow one of your elements you have mastered to emit from you in a 20ft radius for 1 minute. Anyone who is within 20ft of you for the next minute will take 3d8 of the chosen elements damage at the start of their turn. Additionally, anyone who is not either resistant or immune to the type of damage you chose will become vulnerable to the type of damage you choose while within 10ft of you.
Picking another element will cause the previous element to stop, so you are unable to stack this ability.

Barracks

The Barracks specialises in becoming a walking tank and arsenal. They are capable of directly integrating weapons into their Opus, allowing the user to perform unique weapon attack combinations not normally viable.

Heavy Duty

Due to the Barracks Opus large size, it takes a bit longer to move about. This does not come without some benefit. While wearing your Barracks Opus, your speed cannot go above 25ft outside of magic.
You are able to grapple with a creature of Huge size.

Integrated Weaponry

Starting at 1st level, you can integrate a manner of weapons into your Opus, making it a part of the armor. To integrate a weapon into your armor or remove one, you must spend at least an hour tinkering with your Opus to slot it in the right place.
Once a weapon is integrated into the Opus, you can draw and stow them as many times as you want as free actions. You also cannot be disarmed of the weapons. If a weapon has the loading property, you do not need a free hand to load it.
You can have 4 weapons integrated at once. When a weapon is detached from the opus, you must pass a DC10 Intelligence saving throw. A fail results in the weapon breaking (magic weapons cannot break thus you do not need to make the check with them.
You can integrate a 5th weapon when you reach 6th level,

Fighting Style

At 3rd level, you adopt a particular style of fighting as your specialty. Choose a fighting style from the list of optional features. You can't take the same Fighting Style option more than once, even if you get to choose again. If you are wearing an Opus, you do not gain the benefit of the Mariner fighting style.
Archery: You gain a +2 bonus to attack rolls you make with ranged weapons.
Defence: While you are wearing your Opus, you gain a +1 bonus to AC.
Dueling: When you are wielding a melee weapon in one hand and no other weapons, you gain a +2 bonus to damage rolls with that weapon.
Great Weapon Fighting: When you roll a 1 or 2 on a damage die for an attack you make with a melee weapon that you are wielding with two hands, you can reroll the die and must use the new roll, even if the new roll is a 1 or a 2. The weapon must have the two-handed or versatile property for you to gain this benefit.
Protection: When a creature you can see attacks a target other than you that is within 5 feet of you, you can use your reaction to impose disadvantage on the attack roll. You do not need a shield to use this ability.
Tunnel Fighter: You excel at defending narrow passages, doorways, and other tight spaces. As a bonus action, you can enter a defensive stance that lasts until the start of your next turn. While in your defensive stance, you can make opportunity attacks without using your reaction, and you can use your reaction to make a melee attack against a creature that moves more than 5 feet while within your reach.

Fluid Fighter

Starting at 3rd level, you have spent enough time switching up your integrated weapons that you can now seamlessly combine unorthodox weapons together in on attack string. You can now use your bonus action to make a secondary attack with any weapon that does not have the two-handed property, including ranged weapons. Additionally you can add your Intelligence modifier to the damage of this attack, similar to an attack made with your action.

Pop-out Shield

Starting at 6th level, You have constructed a pop-out shield in your Barracks' bracers that can help defend against one attack every round of action. When you are in your Opus and are targeted by an attack you can use your reaction to increase your AC equivalent to your intelligence modifier. You may activate this ability after finding out the attack roll. This AC increase only applies to the triggering attack and will not be taken into account for any additional attacks you take this round.

Brutal Critical

Starting at 9th level, you can roll an additional weapon damage die when determining extra damage from a critical hit with a melee attack.

Siege Engine

Starting at 11th level, you have developed a way of making your own entrances. When attacking a structure with a melee weapon, you roll twice as many dice.

Lockdown

Starting at 15th level, you can now fortify your Opus giving you brilliant survivability. You can spend an bonus action to use Lockdown. When in Lockdown, you have resistance to all damage until your next turn. This can only be used once per short or long rest.

Extra Attack X2

Starting at 20th level, you can now make 3 attacks as part of your Attack action.