Cruachan have many songs for fans of Tir na n'Og. I can't find them on you tube though.
The album Tuatha Na Gael has some songs describing the battles between the Tuatha, Fir Bolg and Formorians
"The sun shone down on helmets, shields and swords,
Midsummers day-The two armies walked in haodes-
Towards Magh Nai-The Fir Bolg followed their chietains,
And swept towards the Tuatha De like waves crash on the beaches."
Or if you're at war with Vanheim, how about Ard Ri Na Heirann?
"Brian Boru, our last Ard Ri
Led the Gael to victory
Could not stand his countries plight
He removed the vikings from his sight"