Idioms Abound
"Without Gods to invoke, people had to turn to other methods of getting to the point."- Dreo Vis
The common tongue among the explored world is known as Bendilian or Imperial Common, formaly and Impspeak, informally. This is due to The Bendil Empire's declaring all official matters are to be done in the native language of Val the First. Scores of other languages exist and are considered 'Native tongues' by The Empire. But a commonality across all languages is the spread of colloquialisms and idioms. They almost seem to transend regional barriers. For many that are common usage today there exists no written record of how they emerged. Some, mostly those from the time of the Bendil Empire, have known sources of origin. Most, no one knows. Those who declare a reason only offering unsustantiated guesses.
Those who study language have long marveled that such phrases always, whenever it is translated, it is done so accurately contextually. Adherance to these seeminly timeless phrases is done so in an almost religious fashion
Common Phrases
Shadowguard's Oath on it - To make an unbeakable promise
To the Dark with you! - To wish someone to spend an eternity banished with the demons to the Outer Dark
The Guild knows or Only the Guild knows- To declare a question practically unanswerable
Silver Shine on me! - A plea for help or assistance
Demontogue! - Accusation of speaking ill on behalf of someone else
The Night Breeze got them - an unexplained or unsolved death/murder
Copper Capped - to be mad or manic
Be it a Raven Feather or Black Feather be damned! - Willingness to continue even against dire or even impossible odds
Flash the Crest - to try to impress someone in order to gain their interest
Foxbait - to be desired by a playfully clever person
Phoenix Eyes - Speak carefully because others may listen and tell others
Remus friend - to be a demanding friend who lashes out if not pampered
I like the colorful phrases but I think more context would be helpful for some of the idioms. Why are copper caps associated with madness? What do ravens have to do with impossible odds?
As I envisioned the meaning of many are lost to history to the inhabitants of the world. A little quirk of their particular time/space/dimension is that such colloquialisms stay true to original context with no filtering or altering of meaning. Funny enough those two you named are of a few I have written, but not published, origin stories for. TLDR Origins Copper Capped to mean manic or mad came from a family of gingers who were just always on the far side of sane. For generations the members of the Family, Jevions by name, became known for being odd if not outright insane. Curiously most offered no harm or insult to their neighbors but were unashamed in their ways and afflictions. The phrase was originally Copper Capped Jevions. After the family died out it became a reference to the mad or manic as 'Copper Capped' The other one mentioned, 'Be it a Raven Feather or Raven Feather be damned' Is from the time when the Order of Dawn and the Order of Dusk battled. The Order of Dusk had a unique form of Heraldry with different bird feathers representing different levels of investment for either the Order or individual members. Raven Feathers meant Order of Dusk viewed the Battle it was displayed of such import that all forces would be brought to bear. Lightseeker Geian Bex, Order of Dawn, when faced with an entire Hoste of Order of Dusk while guarding a pass that led to to a refuge with a small company declared "Be it a Raven Feather or not we shall not retreat while their are innocents to defend, no matter the odds." So a brief snippet of meaning for those. I hope to eventually do full articles on each the named idioms and link them to their origin stories.