"The White Sybil" by Clark Ashton Smith

Sybil: any of several prophetesses usually accepted as 10 in number and credited to widely separate parts of the ancient world (such as Babylonia, Egypt, Greece, and Italy)

ignescent: bursting into flame; emitting sparks of fire when struck with steel

chaffer: could mean to haggle, but here more likely used as a synonym for chatter. Not sure why the alliteration was so important right here, but that appears to be all the author was going for.

eider is a real word, it's a type of seaduck, but it's not obvious to me that the author meant here in that way. He probably thought he was making up a word, as the mountain folk would be quite unlikely to be trading in ocean fowl.

damaskeening is also a real word, but having to with decorative patterns on a watch, or more generally to inlay with gold or silver.

machicolations: an opening between the supporting corbels of a projecting parapet. What's that, eh? It's a castle thing. There was a fun (friendly) controversy over the pronunciation of this word between lindeybeige, Shadiversity, scholagladitoria, metatron, and maybe a few others outside the main core of the so-called "community of the sword". If you have an hour to kill, it might be entertaining to look it up :) I went with Shad's pronunciations. Shad has at least one video completely dedicated to what these things were and how they were used, so if you really want all the gory details, check out his channel. Or if you just like castles in general, check out his channel. Scholagladitoria for swords and sword fighting. Metatron for things to do with ancient Rome and Japan, and with linguistics. Lindeybeige for all manner of history, sword, and tank stuff. There are other channels in the community besides, you will discover them soon enough as you explore these channels.

welkin: the celestial abode of the gods

To follow along: http://www.eldritchdark.com/writings/short-stories/245/the-white-sybil