Isabellae: The Dark Song of the Fomorian Gods (Isabellae #5)

In an effort to defeat the English invaders and their Norman mercenaries and free their island from the yoke of the Crown, the druids of Ireland strike an unholy alliance with fearsome entities summoned from the darkness: the ancient Fomorian gods and their armies. Surrounded by monsters of unprecedented power, Isabellae, her friends, the Irish people and the English forces unite to wage the battle of their lives and save humanity from a horrific fate.