Dwarfs, Dwarves, and Dwarrow

Dwarves are natural engineers. Or rather, a better understanding might be, they are unnatural engineers. Dwarves have a natural understanding of mechanisms and devices, they have an instinct to construct, maintain, and repair. They are also extremely hardy and prefer to live in cramped tunnels. Given that this is "fantasy Dwarf" that appears mechanically in so many games, I set out to try and make a why behind this.

Inspired by Scrap Princess's reimaginings, the Bromeliad, and Discworld Dwarves

D&D: Dwarves and Devices

Dwarves love devices, they love mechanisms and technology. They tend to be inspired by mills, and locks, and really any sort of object or tool with moving parts. They are excellent at maintaining such things, work well with metals and mining (indeed all craftsdwarfship is always of the highest quality). However, they weirdly do not seem to invent anything of their own. Only very rarely will a Dwarf create a new mechanism (perhaps once in a generation), however that mechanism will be lovingly maintained and run essentially forever. However, Dwarves do not generally rely on innovation, but rather the exploitation of ancient and mysterious machines known colloquially as Devices.

Dwarven Devices are of mysterious and huge power, but often now terribly clear on what their purpose is. Dwarves are expert at maintaining, repairing, and (most importantly) repurposing these strange things to suit their own ends. Very rarely will a Dwarf allow a Device to be in the possession of a non-Dwarf. However, there have been notable exceptions. The waterworks of the Imperial capital, for example, are powered by such a Device. Devices, when they are found, are generally found deep in the crust of the planet. In the depths of coal seams, or at the bottom of sea beds. They can also be found in the ruins of ancient Dwarven holdfasts destroyed in war (as the Dwarves would never willingly abandon such treasures).
  

Possibly a Device, possibly time travel

Dwarves largely categorise Devices into two groups: Mānaḫtubutu (lit. The thing that toils) and Abutubarû (lit. The thing that oversees). Of the two, the Mānaḫtubutu are more likely to be seen. Although particularly complex arrangements will involve combinations of many different Mānaḫtubutu Devices, and one or two Abutubarû.

The Thing from Truckers, presented here for no real reason

Dwarves were a great part of the kingdom of the Sorcerer King Sardanapalus, the Dwarven language is closely related to Akkadian. The cities of Sardanapalus' Empire utilised many Devices, and although the ruins have been largely picked clean in the centuries since, there is always a chance that some remain in a previously inaccessible chamber.

Dwarven Modifications
Dwarves sometimes suffer from a sort of madness, which Dwarves seem to interpret as divine. The symptoms are invariably the same: the Dwarf will feel irrationally dissatisfied with some part of their body, and endeavour to remove it. After this, they will craft an artificial replacement part. All this takes place in a sort of manic state or fugue-like trance. These prostheses (and those Dwarves who sport them) are held in great reverence by Dwarven society. These could be as simple as a hook in place of a hand, but given access to greater resources and specifically Devices, they can create replacement parts for themselves superior (or at least more specialised to a particular task) than their original body part. The ideal Dwarf would be a Dwarf who had successfully replaced all their body with artificial components. Despite the social esteem, Dwarves will only craft new limbs/parts when the madness strikes them, otherwise they lack the inspiration to do so (as if a part of their brain is walled off, or perhaps some form of native magic).

Once a Dwarf has removed a piece of themselves, they may keep tinkering with the prosthesis, adapting and upgrading it. For instance, if a Dwarf removed their hand and replaced in with a metal claw (better for climbing, and for delicate work cleaning and carving gems), they could later replace it with rudimentary pincers, if they transitioned more into metalwork. Or, if they were lucky enough to find a suitable device, create a fully articulated robot hand that would grip stronger than a mortal hand, and could removed to act independently.

Some possible Dwarven body modifications:

Hook Hand: A natural weapon that does 1d8 damage, and a bonus to climbing checks. Also a bonus to tinkering involving delicate carving or intricate mechanisms. You may no longer hold a weapon or tool in this hand

Leg Blades: Double running speed and jumping distances. However, suffer a penalty to climbing checks

Carapace: A black iron carapace welded directly onto where skin once was. Counts as natural plate armour. You may no longer wear any armour, nor clothing other than loose robes

Crystaline Eyes: Replace eyes with crystalline obs that allow for increased ranges of spectrum and/or magnification. Requires specific devices.

Hookshot Arm: May fire a repelling line to automatically winch you to another point within 100'. As a weapon it does d6 damage at range. Requires a specific device to build

Dwarves in Mines

Dwarves love to mine. They have a natural affinity for metals and ore, both extracting them and crafting them into useful shapes. Dwarves will mine just about any mineral and find a use for it. From coal in furnaces, to crystals in lenses, to iron for just about anything. Dwarves make superior grade steel, knowing the inherent magics of the material.
  Dwarves seem to be built for living in the cramped and dangerous conditions of mines, being hardy enough not to succumb to toxic vapors and miasmas, resilient enough to survive minor cave ins, have an instinct for direction in tunnels, an ability to see in complete darkness, and can survive quite happily off the variety of fungi, lichen, and blind cave creatures that are the sources of nourishment in the darkness.

The God of the Dwarves

Dwarven religion, often incorporated into the human religion, is monotheistic although not exclusively so. Dwarves throughout history have maintained that although there may be many gods, there is but one god of the Dwarves. Dwarvish beliefs mesh well with strictly monotheistic faiths, although their attitude towards God is somewhat unique. More than anything else, Dwarves fear their God. God is powerful, terrible, and vengeful. God can be placated, with ritual, with proper behaviour, with prayer, but it would be hard to say if the Dwarves worship God.

When incorporated into monotheistic human religions, Dwarves will identify their God as the God (and whatever name is ascribed to them), however in Dwarven temples, or if the Dwarves are incorporated into a polytheistic religion, the God of the Dwarves is known as Armok. The Dwarvish word for their people is Notharmok. Armok knows all and sees all, Armok demands toil, Armok demands sacrifice.

Dwarven Carving of Armok

Dwarf Fortresses

Although Dwarves have many mines, holdfasts, and other structures in which they dwell and toil, coming in all shapes and designs, there is only one type of true Dwarf Fortress. These are where the Dwarves find the majority of their prized Devices. This is where they truly feel they belong. Lodged deep within the crust of the planet, there remain massive sections of the Tomb Ship of the Lich King. Even these fragments and shards of that great vessel are large as palaces and towns. They are made of mysterious black iron, are honeycombed with secret passages and hatchways and unknown traps.

Most Fortresses have been well explored by the Dwarves, and these settlements extend into the surrounding rock with the black iron chunk at the core. However, some are too large even for their devoted inhabitants to have explored fully, some have not yet been discovered, and some that were once thriving fell silent seemingly overnight. Succumbing to some unknown terror that dewlls within the depths of such places.

Sweet! Free Dwarf Fortress!

Rules Malarky

Hardy Constitution
Dwarves begin with +1 to their Constitution modifier. Dwarves can never die of alcohol poisoning.

Craftsdwarfship
Given half a day and appropriate materials, a Dwarf can mend all notches of damage from any piece of equipment. Given access to a forge or workshop the time spent is an hour.

Mining Expertise
Dwarves have a natural direction sense underground, and are considered to have a 3 in 6 in Bushcraft when underground. They also have infravision (similar to seeing through night-vision goggles)

Dwarven Devices
If a Dwarf ever comes into the possession of a Device and wishes to re-purpose it, they have an automatic success in tinkering.

Dwarven Body ModificationEvery level, a Dwarf may (given the right materials) upgrade themselves with an adaptation, or refit an extant prosthetic.