Living metal

Living metal is a tiny modular organism that is used as a resource, making it one of the ingredients of Dwarven Steel. Living metal gets its name from its attributes: the creatures are apparently extremely heat-resistant and impact-resistant, to the point of surviving even being forged like normal metal, and re-establish their bonds when broken off and in close proximity. As such, a sword forged from living metal that gets broken somehow can be repaired without needing to be reforged, as the living metal particles will reattach themselves to each other as long as the two pieces are in close enough proximity.

Living metal in its purest form is naturally soft and not very suitable to make armour and weaponry, but any alloy that features living metal has a pykrete-like quality: making an alloy of soft copper and equally soft living metal produces a much harder alloy that is akin to bronze. Likewise, Dwarven Steel - an alloy whose ingredients also include living metal - is known for its hardness and durability (in addition to the self-repairing quality it inherits from living metal), making it the favoured material for making high-quality armour and weaponry.

Reproduction
Living metal reproduces naturally by absorbing any adjacent metal particles and chunks and spreading its colonies, however this process is very slow. It is said that a longsword made out of an alloy that consists of 99% iron and 1% living metal gradually increases its own living metal composition on its own, and it takes around 1200 years to go from 1% living metal to 100% living metal - at least theoretically. However in reality, this new living metal is not the same pure living metal that is mined and reproduced from the origins, but instead a new form of living metal that takes on some of the qualities of the metal it absorbs. Living metal also reproduces relatively fast (as in, months as opposed to hundreds of years) among oxidized metals such as rusty iron, making intentionally rusting metal dust to quickly reproduce living metal a favourite method of growing them fast.

Living metal also appears to reproduce on its own in the two deposits that it naturally appears in, by growing on sacred trees that don't grow anywhere else.

Deposits
Naturally-formed living metal can only be found in Northern Etrand, and in only two deposits: two small plateaus where certain trees sacred to the Dwarven Religion grow and appear to produce living metal as their "fruit". over time, ravines has formed around the sacred trees, making it unsafe to access them, but also forming a natural place of storage for the products of the trees: the living metal particles would drop down to the ravines, where they would be drifted and washed into nearby caves.

Since only these two deposits exist, the Dwarves are very careful about mining them, making sure that the mines never have to be closed. Before the Etrandish annexation of the Dwarven clans, many wars were fought between the clans for control over these deposits.