Metal; It’s Lack Of Use
Before Feathersmithing can be described, the strange status of Metal in the Eclipsed Kingdoms must be discussed.
1. Fey Ancestry
Ever since the Sleeping King was awake, and perhaps earlier, the chivalry of the Eclipsed Kingdom have interbred with. Several noble houses are Half-Elven and even most common people often have a drop of Fey blood. The touch, taste and, in some cases, the mere presence of Cold Iron is deeply disagreeable to these individuals. Although alloys like Bronze are regarded as less unpleasant there is no fashion for metal armour amongst the Fey-blooded and many will regard its presence as an insult and a threat (precisely the reason the Iron Men prefer it).
2. The Churl Beast
The creature called the 'Rust Monster', while rare in other realms, has always been relatively common in the Eclipsed Kingdom. It is popularly known that, if a metal weapon or tool is left for long enough and rusts completely under the earth, a baby Churl Beast will hatch from it.
|A Churl Beast|
3. Rust Bloods
(See 'human races’). Whether Rust Bloods exist as a result of Fey Ancestry or as a result of Churls becoming too intimate with their beasts over several generations, they present another barrier as, if they are the target of metal weapons, they may decay them when struck, and if they seek to make use of metal armour, they may destroy their own protection by bleeding on it.
4. Magnetic Sands
The Iron Sands to the south of the Eclipsed Kingdom where the Bottle Knights and the Emir of Crows range across the red dunes are, in some places, partially magnetic. This presents a challenge for the metal-clad knight. These sands are sometimes collected and sold, they can be placed in bags and used as handy 'spoiling weapons' against those who wear or wield metal as a tool.
5. Acidic Rain And Microwave Storms
The weather and pressure fronts that emerge and condense while the black form of Azathoth is in the sky, blotting out the sun, often have unusual effects. Rains from these storms are mildly acidic and cause various complex kinds of rust and decay (see Rust - a peasant obsession), there are also seasonal winter Microwave storms emanating from the body of the black god causing water-based beings to suffer heatstroke in the snow and making all metal arc with dangerous sparks.
Metal; It’s Occasional Use
Despite all of this, metal is still occasionally used in weapons and armour. It is an extremely cheap and easily worked material. Arms and armour are often brought in from outside the kingdom and if a foreign noble of high status wears it then a knight can hardly ask them to abandon it. It must have been in more use in the past as Barrow Mounds and the battlefields of the Apocalypse War have huge metal deposits and, while it is noxious to Fey, it is also very useful against Fey and while no decent Lord would be see using it for that purpose, they could certainly have the occasional piece lying about, and if they were attacked by wild criminal fey, and if they happened to use to to defend themselves, who could argue? Peasants are allowed to wield weapons (one per household) and some have swords or hunt with metal-tipped arrows. It can be useful in armouring men-at-arms cheaply and forest criminals often use fragments of it.
(Side Note; Decay - A Peasant Obsession)
Since there is almost nothing entertaining or interesting for a Peasant to do, and with the active encouragement of the Black Church, who view contemplation of decay as a reasonable form of lay-worship of the Black God, the Peasant or Churl class of the Ecllipsed Kingdom have developed an obsession with, and complex folklore of, Rust.
Finally we come to the primary point.
Attaining Feathersmithed Work
Feathersmithed arms and armour can only be produced by the Goblinish savants of the Eclipsed Kingdom, each piece is an individual work of art for a particular person. The price for the construction of a piece of feathersmithed armour is usually significant either in coin, broken hearts, service or simply impossible conceptual items (a worms cough, for example).
The standard rule of enchantment is that the more frail, brittle, expensive and rare a material is, the more powerful the enchantment that can be cast on it. The more of its strength and force the item receives from its actual material form, the less powerful the magic and the lower the status.
A popular mail equivalent is a hauberk of autumn leaves held together with thorns. Mail of rose petals or water-lily petals. Spider-webs kept whole and attacked at the web-ends with the spiders own broken limbs are an expensive mail. Snake skins with the heads left dangling can make a savage 'wild mail' and glass beads are a cheap version.
It's rare for knights to wear a full-head helm of any kind. Feathersmithed Crowns or Circlets fill the same role. Crowns of Flowers, crowns of thorns and crowns of Ice are popular. Masks of crystal, of carved ebony or bone, of ceramic and of glass will only protect the front of the face (a True Knight should always be head-on to their enemies anyway so this is acceptable).
‘Full’ Gothic plate is incredibly rare and most knights wear a breastplate, along with some vambraces and greaves, over mail.
We might therefore imagine a 'Common' Knight of the low nobility wearing a hauberk of autumn leaves with a painted stoneware plate, a shield of silver birch bark and a paper sword with a common poem by a Monk of St Gorgoth.