So I'm working on a fantasy novel, based on my love of Norse and Celtic mythology. And heavy metal. It's called "Therial's Song".
I'm reading a book right now, by Barry Cunliffe, one of the big academic mucky-mucks when it comes to the Celts. And guess what? It turns out the Cimmerians were a real people!
Most people know the Cimmerians from Robert E. Howard; everyone's favorite barbarian, Conan, was a "Cimmerian", a vaguely Germanic/Celtic people living of the periphery of the great civilizations of Hyboria.
The real Cimmerians inhabited the Pontic Steppe, the huge expanse of plains on the northern fringe of the Black Sea. Apparently, in the dim mists of antiquity, the Scythians chased them out of their homeland, into the Danube River basin, where the mingled with the indigenous "Urnfield" culture, transmitting their advanced knowledge of horsemanship, contributing to the rise of the Halstatt culture...
...and as we all know, the Hallstatt people were the proto-Celts! In other words, the real-life Cimmerians may have contributed to the culture of the real-world Celts!
Reading about the ancient Celts is totally fascinating. Cunliffe's book is a little dry, and I wish he'd included more pictures of the stuff he discusses, but it's still a worthy read.