Celtic myths you'd like to see more in novels?

I'm writing a story based loosely around Celtic mythology, and I'd like to know what kind of things you guys think would be cool to include. Gods, goddesses, specific myths, versions of specific myths, mythological creatures, curses, etc.

So far, I've got a series of gods and goddesses including the Morrigan, Macha, and Badb/Nemain, Rhiannon, Dana, the Dagda, Epona, Brighid, Cernunnos, Herne, and Lugh. From mythological creatures I've got the Dearg Due, The Dullahan, banshees, kelpies, selkies,
Sídhe, and Redcaps.

Cu Chulain and Fionn mac Cumhaill, for sure, if you want some folk hero stuff. And Scathach if you like badass warrior ladies.

Oh, I totally forgot to mention Chu Chulain!

And I looked into those other two, and they're really cool! Thanks :)