Oh man where do I even begin.
Short explanation? It's a worldbuilding project centered on culture and language. Not clear enough? Then brace yourself.
The Cradle of Songs is my main project, which I've poured a good portion of my life into. All of the things that I know about culture and language I've learned by working on this.
To me, it's much more than just worldbuilding. Rather, I feel like I've created a little universe. I think calling it a "project" falls short on what this actually is, too. So usually I say that CoS is a collection of projects. You can learn more about it on the (WIP) wiki! (hosted by the wonderful people at Miraheze)
The Cradle of Songs
Classical to medieval history
A good part, though not the bulk, of my worldbuilding centers around the classical and medieval eras of World. This includes characters such as Tyll Cwallgun, national hero of Amrhyl, and Heranāō, the prophetess of the Heranist religion. But I don't focus on character writing during this period. Instead, most of my work here is on language and religion.
Jotunnheim
Jotunnheim (affectionately yoderheim) is a collaborative worldbuilding project I'm currently involved with. At its core it's a steampunky-dieselpunky-WWI-vibed history-centered project, although there's also a heavy emphasis on language and culture creation, with some minor spec bio stuff thrown in for good measure.
Currently, my main and only country is one located in the continent of Anschuhe, the Great Queendom of the Rising Shouting Sun, or RSS for short (excuse the barebones page, I swear I've done more than this).
The Copper War
The central conflict, which acts as the main theme of Jotunnheim, is the Copper War, also called the Great War. Not unlike our own Great War, it was the deadliest conflict in all of Jotunnheim history. It resulted from diplomatic and economic tensions, mostly caused by the increased demand for copper (thus the name) for use in the manufacturing and maintaining of heavy weaponry. Tanks, mechs, ships, airships, you name it. At the time, Tschintiessteiss (TSC for short) had a chokehold on the copper trade, being very rich in the material, and as such prevented any other major power, mainly Dhimrai, from gaining any share from it, which led to a long, bitter economic conflict that escalated into all out war in the year 4602 CY.
This conflict ended in 4607 CY, and is thus canonically already in the past. Nevertheless, its effects are still felt worldwide to the present day.