Ironwolfe (The Triads of Tir na n'Og, #1)

When he crosses into Tir na n'Og, Janos Narodniho, known to history as Ironwolfe, a Voivode in the infamous Black Army of Mathias Corvinus, finds himself bound in service to the mighty Sidhe, the Fey who rule over all mankind through their human agents, the Triads. For the first time in his illustrious and bloody career, the Ironwolfe is ensnared in events from which he cannot trick, think, or fight his way free...while the futures of his own world and Tir na n'Og hang in the balance. Book ...