Exotic Materials
While the majority of weapons and armour are made of common metals and wood, adventurers will frequently find cause to invest time, energy and money into acquring equipment made of more esoteric materials. Where weapon costs are noted, you can apply that material to twenty pieces of ammunition such as arrows or bolts for the same costs. Any sufficiently large city should be able to procure all of the materials listed, however smaller towns or villages may struggle with some of the especially costly ones.
Existing pieces of weapons or armour can be reforged for the cost listed, which includes the cost of the materials. If the character can provide the materials, reduce the cost by 50%. At a DM's discretion two or more materials can be combined for one item (for instance a darkwood spear with a dragonbone tip) however it should be assumed that each material is 'standalone' and cannot be mixed.
Adamantine
Description: Adamantine is an extremely hard, black metal. In its finished form, adamantine metal reflects a clear green sheen under candlelight, and purple-white under magical light. In its smelted form it weighs roughly the same amount of steel, but is far more resilient to damage.
Weapons: Whenever an adamantine weapon or piece of ammunition hits an object, the hit is a critical hit.
Cost: 500gp
Armour: While you're wearing armour forged from Adamantine, any critical hit against you becomes a normal hit.
Cost: 1000gp
Ankheg
Description: Enormous predatory burrowing insects, ankhegs are feared as for their powerful mandibles, strong armour plating and searing acidic spit. Adventurers who slay an ankheg may find use for all of
Armour: Ankheg chitin plates can be crafted to fulfill a role similar to that of metallic armour. The tiny barbs that cover the plates mean that while wearing this armour if you grapple or are grappled by another cretaure, that creature takes 1d6 piercing damage at the start of your turns as long as the grappling persists.
Cost: 3000gp
Celestial Steel
Description: Originating from the upper planes, celestial steel gleams silvery-gold when lit. Its innate properties allow it to enhance any healing magic.
Weapons: Any metal weapon can be forged with celestial steel. When wielding a weapon made from this material, any healing spell you cast adds your proficiency bonus to the hit points restored.
Armour: Any metallic armour can be forged with celestial steel. If you are affected by a spell or magical effect that restores hit points while wearing this armour, you additionally gain half the amount restored by the spell or effect at the end of your next turn.
Cost: 1000gp
Darkwood
Description: This rare wood is light and flexible making it ideal for weapons and armour. As the name implies its a much darker shade of colouration, approaching black.
Weapons: Weapons made of darkwood weigh half as much as normal wooden weapons, and they cannot catch fire, even while unattended. They also gain the finesse property, so long as they are wielded in one hand.
Cost: 450gp.
Armour: Any metallic armour such as half-plate or plate mail can be crafted from ironwood. This allows any druids who may have qualms regarding metal armour to wear it, as well as negating the Heat Metal spell. The weight of darkwood armour is reduced by half compared to its metallic counterpart, and they cannot catch fire, even while unattended.
Cost: 200gp.
Dragonbone
Description: Dragonbones retain their connection to the magical energies that pervade the majestic beasts of legend and lore, making them highly prized as materials. A single dragon's corpse can outfit multiple squads, but doing so tends to make enemies of dragonkind in the process. Despite this, a fair number of adventurers will choose to wield dragonbone equipment, unable to look past its boons.
Weapons: Weapons and ammunition crafted from dragonbone and dragonfangs are especially potent. Despite being non-magical in nature the weapons have a +1 to attack rolls, and deal 1 additional damage of the damage type matching the breath weapon from the dragon the bodyparts came from. Magical dragonbone weapons cannot exceed a +3 bonus to attack rolls, even if they otherwise have a +3 enchantment.
Cost: 1500gp
Armour: Armour crafted with dragonbone is especially good at deflecting ranged attacks. You have an additional +1AC against any ranged weapon and spell attacks. Magical dragonbone armour cannot exceed a +3 bonus to armour class, even if they otherwise have a +3 enchantment.
Cost: 5000gp
Dragonscale
Description: Properly harvested dragonscales are highly prized, as they retain a degree of the protection that the dragon had in life. Unfortunately dragons aren't usually willing to give up their scales, and so acquiring them can be quite costly.
Armour: Armour crafted from dragon scales grants resistance to the damage type of the breath weapon that the originating dragon had. Red dragonscale armour, for example, would give resistance to fire damage. Shields made from dragonscales allow you to use your Reaction to throw up your shield to gain resistance to that damage type until the start of your next turn.
Cost: 10000gp (Shields: 5000gp)
Elementium
Description: Elementium ore's origins aren't known, though the most common theory is that it comes from the elemental planes. When forged into weapons or armour elementium steel is able to absorb excess elemental energies that can then be released in your favour. Items made from elementium are usually wildly colourful, with interconnecting patterns and swirls of fiery reds, icy blues, gleaming whites and dark ashen blacks.
Weapons: When you cast a spell of first level or higher that deals fire, cold, thunder or lightning damage while wielding a weapon forged of elementium your weapon becomes charged with the same element until the end of your next turn. If you hit with an attack with the weapon it deals 1d8 of the corresponding damage type. The energy is then expended. Elementium weapons can only hold one energy type at a time.
Cost: 2000gp
Armour: If you take fire, cold, thunder or lightning damage while wearing elemenitum armour, it retains a fragment of the elemental power. When a creature within 5 feet of you hits you with a melee attack, armour erupts with the elemental energy, dealing 1d8 of the corresponding damage type. The energy is then expended. Elementium armour can only hold one energy type at a time.
Cost: 2000gp
Ironwood
Description: Ironwood was originally a short-lived magical creation devised by druids, but over time, they managed to cultivate ironwood trees that grow naturally. When under certain lights, it may almost seem to have a metallic sheen on the bark. Ironwood is much tougher than 'normal' woods, and has been used in the production of both weapons and armour.
Weapons: Bows and crossbows made from ironwood are much sturdier, allowing for more powerful draws. This allows you to add your strength modifier to damage rolls, though a negative strength modifier will likewise lower damage done. Ammunition such as arrows and bolts made from ironwood do not shatter, allowing them to be recovered at a 100% rate after battle, instead of the usual 50%.
Cost: 650gp
Armour: Any metallic armour such as half-plate or plate mail can be crafted from ironwood. This allows any druids who may have qualms regarding metal armour to wear it, as well as negating the Heat Metal spell. Fire damage taken while wearing ironwood armour is reduced by the amount of AC above 10 that the armour grants you, to a maximum reduction of halving the damage, before applying resistances.
Cost: 1300gp
Mithral
Description: Mithral is an exceedingly light metal for its strength. In its raw form it appears as a silver-and-black mineral, and becomes a shining silvery-blue when it forged.
Weapons: Metal weapons crafted from mithral gain the Finesse property if they didn't already have it, as long as wielded in one hand.
Cost: 450gp
Armour: If the armor normally imposes disadvantage on Dexterity (Stealth) checks or has a Strength requirement, the mithral version of the armor doesn't.
Cost: 750gp
Silver
Description: Widely used in currency, jewellery, decorations and more, silver is also uniquely potent against certain creatures including lycanthropes, wraiths and some devils. As such many an adventurer has found themselves in need of a silvered sword or breastplate at one time or another to supplement their offense and defense.
Weapons: Some monsters that have immunity or resistance to nonmagical weapons are susceptible to silver weapons, so cautious adventurers invest extra coin to plate their weapons with silver.
Cost: 100gp
Armour: Creatures whose damage resistance is bypassed by silver have disadvantage when trying to make attacks against you while you wear silvered armour.
Cost: 350gp