Coblyn (coblynau / coblynod)

No mythic origin tale is recorded in the supplied sources. Lexically, Salesbury's 1547 Welsh–English dictionary records koblyn translating to "a goblin," and modern summaries state the word is related to English "goblin" and may derive via French Gobelin from a Germanic source akin to German Kobold. Beyond this etymological placement, the supplied material does not give a traditional creation or founding narrative for coblynau.

Described as short (between half a yard tall and just shorter than humans), very ugly, and often dressed in miner's clothing while carrying tools which they use to imitate mining work ineffectually. An anecdotal surface sighting recorded a group of fifteen to sixteen coblynau dressed in red with yellow-spotted red handkerchiefs around their heads, one individual described as having a copper-coloured face; this is reported as a single field account rather than a universal costume.

Coblynau produce a peculiar knocking sound underground which miners interpret as indicating rich veins of ore or treasure. They imitate mining labor enthusiastically but ineffectually, and are generally considered helpful or "friendly fairies" and a source of good luck to miners. They are morally responsive: they may cease their helpful knocking if miners appear overly greedy, and may throw rocks at miners if disrespected—these actions are described as annoyances rather than seriously harmful attacks.